diff --git a/doc/source/admin/components.rst b/doc/source/admin/components.rst
index 3bec28a..18bbfa3 100644
--- a/doc/source/admin/components.rst
+++ b/doc/source/admin/components.rst
@@ -408,7 +408,7 @@
       Path to command socket file for the executor process.
 
    .. attr:: finger_port
-      :default: 79
+      :default: 7900
 
       Port to use for finger log streamer.
 
@@ -451,13 +451,6 @@
 
       SSH private key file to be used when logging into worker nodes.
 
-   .. attr:: user
-      :default: zuul
-
-      User ID for the zuul-executor process. In normal operation as a
-      daemon, the executor should be started as the ``root`` user, but
-      it will drop privileges to this user during startup.
-
    .. _admin_sitewide_variables:
 
    .. attr:: variables
diff --git a/doc/source/admin/drivers/zuul.rst b/doc/source/admin/drivers/zuul.rst
index d95dffc..41535ee 100644
--- a/doc/source/admin/drivers/zuul.rst
+++ b/doc/source/admin/drivers/zuul.rst
@@ -26,6 +26,12 @@
          When Zuul merges a change to a project, it generates this
          event for every open change in the project.
 
+         .. warning::
+
+            Triggering on this event can cause poor performance when
+            using the GitHub driver with a large number of
+            installations.
+
       .. value:: parent-change-enqueued
 
          When Zuul enqueues a change into any pipeline, it generates
diff --git a/requirements.txt b/requirements.txt
index 39a2b02..193c64e 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -25,5 +25,6 @@
 cachecontrol
 pyjwt
 iso8601
+yarl>=0.11,<1.0
 aiohttp
 uvloop;python_version>='3.5'
diff --git a/tests/base.py b/tests/base.py
index 59c0d2a..c449242 100755
--- a/tests/base.py
+++ b/tests/base.py
@@ -170,7 +170,7 @@
             'status': status,
             'subject': subject,
             'submitRecords': [],
-            'url': 'https://hostname/%s' % number}
+            'url': 'https://%s/%s' % (self.gerrit.server, number)}
 
         self.upstream_root = upstream_root
         self.addPatchset(files=files, parent=parent)
@@ -559,14 +559,13 @@
             return change.query()
         return {}
 
-    def simpleQuery(self, query):
-        self.log.debug("simpleQuery: %s" % query)
-        self.queries.append(query)
+    def _simpleQuery(self, query):
         if query.startswith('change:'):
             # Query a specific changeid
             changeid = query[len('change:'):]
             l = [change.query() for change in self.changes.values()
-                 if change.data['id'] == changeid]
+                 if (change.data['id'] == changeid or
+                     change.data['number'] == changeid)]
         elif query.startswith('message:'):
             # Query the content of a commit message
             msg = query[len('message:'):].strip()
@@ -577,6 +576,20 @@
             l = [change.query() for change in self.changes.values()]
         return l
 
+    def simpleQuery(self, query):
+        self.log.debug("simpleQuery: %s" % query)
+        self.queries.append(query)
+        results = []
+        if query.startswith('(') and 'OR' in query:
+            query = query[1:-2]
+            for q in query.split(' OR '):
+                for r in self._simpleQuery(q):
+                    if r not in results:
+                        results.append(r)
+        else:
+            results = self._simpleQuery(query)
+        return results
+
     def _start_watcher_thread(self, *args, **kw):
         pass
 
@@ -628,6 +641,7 @@
         self.is_merged = False
         self.merge_message = None
         self.state = 'open'
+        self.url = 'https://%s/%s/pull/%s' % (github.server, project, number)
         self._createPRRef()
         self._addCommitToRepo(files=files)
         self._updateTimeStamp()
@@ -1605,6 +1619,8 @@
             data['username'] = 'fakeuser'
         if 'windows' in node_type:
             data['connection_type'] = 'winrm'
+        if 'network' in node_type:
+            data['connection_type'] = 'network_cli'
 
         data = json.dumps(data).encode('utf8')
         path = self.client.create(path, data,
diff --git a/tests/fixtures/config/cross-source/git/common-config/playbooks/nonvoting-project-merge.yaml b/tests/fixtures/config/cross-source/git/common-config/playbooks/nonvoting-project-merge.yaml
new file mode 100644
index 0000000..f679dce
--- /dev/null
+++ b/tests/fixtures/config/cross-source/git/common-config/playbooks/nonvoting-project-merge.yaml
@@ -0,0 +1,2 @@
+- hosts: all
+  tasks: []
diff --git a/tests/fixtures/config/cross-source/git/common-config/playbooks/nonvoting-project-test1.yaml b/tests/fixtures/config/cross-source/git/common-config/playbooks/nonvoting-project-test1.yaml
new file mode 100644
index 0000000..f679dce
--- /dev/null
+++ b/tests/fixtures/config/cross-source/git/common-config/playbooks/nonvoting-project-test1.yaml
@@ -0,0 +1,2 @@
+- hosts: all
+  tasks: []
diff --git a/tests/fixtures/config/cross-source/git/common-config/playbooks/nonvoting-project-test2.yaml b/tests/fixtures/config/cross-source/git/common-config/playbooks/nonvoting-project-test2.yaml
new file mode 100644
index 0000000..f679dce
--- /dev/null
+++ b/tests/fixtures/config/cross-source/git/common-config/playbooks/nonvoting-project-test2.yaml
@@ -0,0 +1,2 @@
+- hosts: all
+  tasks: []
diff --git a/tests/fixtures/config/cross-source/git/common-config/playbooks/project-merge.yaml b/tests/fixtures/config/cross-source/git/common-config/playbooks/project-merge.yaml
new file mode 100644
index 0000000..f679dce
--- /dev/null
+++ b/tests/fixtures/config/cross-source/git/common-config/playbooks/project-merge.yaml
@@ -0,0 +1,2 @@
+- hosts: all
+  tasks: []
diff --git a/tests/fixtures/config/cross-source/git/common-config/playbooks/project-post.yaml b/tests/fixtures/config/cross-source/git/common-config/playbooks/project-post.yaml
new file mode 100644
index 0000000..f679dce
--- /dev/null
+++ b/tests/fixtures/config/cross-source/git/common-config/playbooks/project-post.yaml
@@ -0,0 +1,2 @@
+- hosts: all
+  tasks: []
diff --git a/tests/fixtures/config/cross-source/git/common-config/playbooks/project-test1.yaml b/tests/fixtures/config/cross-source/git/common-config/playbooks/project-test1.yaml
new file mode 100644
index 0000000..f679dce
--- /dev/null
+++ b/tests/fixtures/config/cross-source/git/common-config/playbooks/project-test1.yaml
@@ -0,0 +1,2 @@
+- hosts: all
+  tasks: []
diff --git a/tests/fixtures/config/cross-source/git/common-config/playbooks/project-test2.yaml b/tests/fixtures/config/cross-source/git/common-config/playbooks/project-test2.yaml
new file mode 100644
index 0000000..f679dce
--- /dev/null
+++ b/tests/fixtures/config/cross-source/git/common-config/playbooks/project-test2.yaml
@@ -0,0 +1,2 @@
+- hosts: all
+  tasks: []
diff --git a/tests/fixtures/config/cross-source/git/common-config/playbooks/project-testfile.yaml b/tests/fixtures/config/cross-source/git/common-config/playbooks/project-testfile.yaml
new file mode 100644
index 0000000..f679dce
--- /dev/null
+++ b/tests/fixtures/config/cross-source/git/common-config/playbooks/project-testfile.yaml
@@ -0,0 +1,2 @@
+- hosts: all
+  tasks: []
diff --git a/tests/fixtures/config/cross-source/git/common-config/playbooks/project1-project2-integration.yaml b/tests/fixtures/config/cross-source/git/common-config/playbooks/project1-project2-integration.yaml
new file mode 100644
index 0000000..f679dce
--- /dev/null
+++ b/tests/fixtures/config/cross-source/git/common-config/playbooks/project1-project2-integration.yaml
@@ -0,0 +1,2 @@
+- hosts: all
+  tasks: []
diff --git a/tests/fixtures/config/cross-source/git/common-config/zuul.yaml b/tests/fixtures/config/cross-source/git/common-config/zuul.yaml
new file mode 100644
index 0000000..abdc34a
--- /dev/null
+++ b/tests/fixtures/config/cross-source/git/common-config/zuul.yaml
@@ -0,0 +1,168 @@
+- pipeline:
+    name: check
+    manager: independent
+    trigger:
+      gerrit:
+        - event: patchset-created
+      github:
+        - event: pull_request
+          action: edited
+    success:
+      gerrit:
+        Verified: 1
+      github: {}
+    failure:
+      gerrit:
+        Verified: -1
+      github: {}
+
+- pipeline:
+    name: gate
+    manager: dependent
+    success-message: Build succeeded (gate).
+    require:
+      github:
+        label: approved
+      gerrit:
+        approval:
+          - Approved: 1
+    trigger:
+      gerrit:
+        - event: comment-added
+          approval:
+            - Approved: 1
+      github:
+        - event: pull_request
+          action: edited
+        - event: pull_request
+          action: labeled
+          label: approved
+    success:
+      gerrit:
+        Verified: 2
+        submit: true
+      github:
+        merge: true
+    failure:
+      gerrit:
+        Verified: -2
+      github: {}
+    start:
+      gerrit:
+        Verified: 0
+      github: {}
+    precedence: high
+
+- pipeline:
+    name: post
+    manager: independent
+    trigger:
+      gerrit:
+        - event: ref-updated
+          ref: ^(?!refs/).*$
+    precedence: low
+
+- job:
+    name: base
+    parent: null
+
+- job:
+    name: project-merge
+    hold-following-changes: true
+    nodeset:
+      nodes:
+        - name: controller
+          label: label1
+    run: playbooks/project-merge.yaml
+
+- job:
+    name: project-test1
+    attempts: 4
+    nodeset:
+      nodes:
+        - name: controller
+          label: label1
+    run: playbooks/project-test1.yaml
+
+- job:
+    name: project-test1
+    branches: stable
+    nodeset:
+      nodes:
+        - name: controller
+          label: label2
+    run: playbooks/project-test1.yaml
+
+- job:
+    name: project-post
+    nodeset:
+      nodes:
+        - name: static
+          label: ubuntu-xenial
+    run: playbooks/project-post.yaml
+
+- job:
+    name: project-test2
+    nodeset:
+      nodes:
+        - name: controller
+          label: label1
+    run: playbooks/project-test2.yaml
+
+- job:
+    name: project1-project2-integration
+    nodeset:
+      nodes:
+        - name: controller
+          label: label1
+    run: playbooks/project1-project2-integration.yaml
+
+- job:
+    name: project-testfile
+    files:
+      - .*-requires
+    run: playbooks/project-testfile.yaml
+
+- project:
+    name: gerrit/project1
+    check:
+      jobs:
+        - project-merge
+        - project-test1:
+            dependencies: project-merge
+        - project-test2:
+            dependencies: project-merge
+        - project1-project2-integration:
+            dependencies: project-merge
+    gate:
+      queue: integrated
+      jobs:
+        - project-merge
+        - project-test1:
+            dependencies: project-merge
+        - project-test2:
+            dependencies: project-merge
+        - project1-project2-integration:
+            dependencies: project-merge
+
+- project:
+    name: github/project2
+    check:
+      jobs:
+        - project-merge
+        - project-test1:
+            dependencies: project-merge
+        - project-test2:
+            dependencies: project-merge
+        - project1-project2-integration:
+            dependencies: project-merge
+    gate:
+      queue: integrated
+      jobs:
+        - project-merge
+        - project-test1:
+            dependencies: project-merge
+        - project-test2:
+            dependencies: project-merge
+        - project1-project2-integration:
+            dependencies: project-merge
diff --git a/tests/fixtures/config/cross-source/git/gerrit_project1/README b/tests/fixtures/config/cross-source/git/gerrit_project1/README
new file mode 100644
index 0000000..9daeafb
--- /dev/null
+++ b/tests/fixtures/config/cross-source/git/gerrit_project1/README
@@ -0,0 +1 @@
+test
diff --git a/tests/fixtures/config/cross-source/git/github_project2/README b/tests/fixtures/config/cross-source/git/github_project2/README
new file mode 100644
index 0000000..9daeafb
--- /dev/null
+++ b/tests/fixtures/config/cross-source/git/github_project2/README
@@ -0,0 +1 @@
+test
diff --git a/tests/fixtures/config/cross-source/main.yaml b/tests/fixtures/config/cross-source/main.yaml
new file mode 100644
index 0000000..bf85c33
--- /dev/null
+++ b/tests/fixtures/config/cross-source/main.yaml
@@ -0,0 +1,11 @@
+- tenant:
+    name: tenant-one
+    source:
+      gerrit:
+        config-projects:
+          - common-config
+        untrusted-projects:
+          - gerrit/project1
+      github:
+        untrusted-projects:
+          - github/project2
diff --git a/tests/fixtures/config/inventory/git/common-config/zuul.yaml b/tests/fixtures/config/inventory/git/common-config/zuul.yaml
index 36789a3..f592eb4 100644
--- a/tests/fixtures/config/inventory/git/common-config/zuul.yaml
+++ b/tests/fixtures/config/inventory/git/common-config/zuul.yaml
@@ -40,6 +40,8 @@
         label: fakeuser-label
       - name: windows
         label: windows-label
+      - name: network
+        label: network-label
 
 - job:
     name: base
diff --git a/tests/fixtures/zuul-gerrit-github.conf b/tests/fixtures/zuul-gerrit-github.conf
new file mode 100644
index 0000000..d3cbf7b
--- /dev/null
+++ b/tests/fixtures/zuul-gerrit-github.conf
@@ -0,0 +1,35 @@
+[gearman]
+server=127.0.0.1
+
+[statsd]
+# note, use 127.0.0.1 rather than localhost to avoid getting ipv6
+# see: https://github.com/jsocol/pystatsd/issues/61
+server=127.0.0.1
+
+[scheduler]
+tenant_config=main.yaml
+
+[merger]
+git_dir=/tmp/zuul-test/merger-git
+git_user_email=zuul@example.com
+git_user_name=zuul
+
+[executor]
+git_dir=/tmp/zuul-test/executor-git
+
+[connection gerrit]
+driver=gerrit
+server=review.example.com
+user=jenkins
+sshkey=fake_id_rsa_path
+
+[connection github]
+driver=github
+webhook_token=0000000000000000000000000000000000000000
+
+[connection smtp]
+driver=smtp
+server=localhost
+port=25
+default_from=zuul@example.com
+default_to=you@example.com
diff --git a/tests/unit/test_connection.py b/tests/unit/test_connection.py
index 4a405fd..c45da94 100644
--- a/tests/unit/test_connection.py
+++ b/tests/unit/test_connection.py
@@ -119,7 +119,7 @@
         self.assertEqual('SUCCESS', buildset0['result'])
         self.assertEqual('Build succeeded.', buildset0['message'])
         self.assertEqual('tenant-one', buildset0['tenant'])
-        self.assertEqual('https://hostname/%d' % buildset0['change'],
+        self.assertEqual('https://review.example.com/%d' % buildset0['change'],
                          buildset0['ref_url'])
 
         buildset0_builds = conn.execute(
diff --git a/tests/unit/test_cross_crd.py b/tests/unit/test_cross_crd.py
new file mode 100644
index 0000000..7d68989
--- /dev/null
+++ b/tests/unit/test_cross_crd.py
@@ -0,0 +1,950 @@
+#!/usr/bin/env python
+
+# Copyright 2012 Hewlett-Packard Development Company, L.P.
+# Copyright 2018 Red Hat, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+from tests.base import (
+    ZuulTestCase,
+)
+
+
+class TestGerritToGithubCRD(ZuulTestCase):
+    config_file = 'zuul-gerrit-github.conf'
+    tenant_config_file = 'config/cross-source/main.yaml'
+
+    def test_crd_gate(self):
+        "Test cross-repo dependencies"
+        A = self.fake_gerrit.addFakeChange('gerrit/project1', 'master', 'A')
+        B = self.fake_github.openFakePullRequest('github/project2', 'master',
+                                                 'B')
+
+        A.addApproval('Code-Review', 2)
+
+        AM2 = self.fake_gerrit.addFakeChange('gerrit/project1', 'master',
+                                             'AM2')
+        AM1 = self.fake_gerrit.addFakeChange('gerrit/project1', 'master',
+                                             'AM1')
+        AM2.setMerged()
+        AM1.setMerged()
+
+        # A -> AM1 -> AM2
+        # A Depends-On: B
+        # M2 is here to make sure it is never queried.  If it is, it
+        # means zuul is walking down the entire history of merged
+        # changes.
+
+        A.setDependsOn(AM1, 1)
+        AM1.setDependsOn(AM2, 1)
+
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.url)
+
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertFalse(B.is_merged)
+
+        for connection in self.connections.connections.values():
+            connection.maintainCache([])
+
+        self.executor_server.hold_jobs_in_build = True
+        B.addLabel('approved')
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(AM2.queried, 0)
+        self.assertEqual(A.data['status'], 'MERGED')
+        self.assertTrue(B.is_merged)
+        self.assertEqual(A.reported, 2)
+        self.assertEqual(len(B.comments), 2)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'gerrit/project1').changes
+        self.assertEqual(changes, '1,%s 1,1' % B.head_sha)
+
+    def test_crd_branch(self):
+        "Test cross-repo dependencies in multiple branches"
+
+        self.create_branch('github/project2', 'mp')
+        A = self.fake_gerrit.addFakeChange('gerrit/project1', 'master', 'A')
+        B = self.fake_github.openFakePullRequest('github/project2', 'master',
+                                                 'B')
+        C1 = self.fake_github.openFakePullRequest('github/project2', 'mp',
+                                                  'C1')
+
+        A.addApproval('Code-Review', 2)
+
+        # A Depends-On: B+C1
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\nDepends-On: %s\n' % (
+            A.subject, B.url, C1.url)
+
+        self.executor_server.hold_jobs_in_build = True
+        B.addLabel('approved')
+        C1.addLabel('approved')
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'MERGED')
+        self.assertTrue(B.is_merged)
+        self.assertTrue(C1.is_merged)
+        self.assertEqual(A.reported, 2)
+        self.assertEqual(len(B.comments), 2)
+        self.assertEqual(len(C1.comments), 2)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'gerrit/project1').changes
+        self.assertEqual(changes, '1,%s 2,%s 1,1' %
+                         (B.head_sha, C1.head_sha))
+
+    def test_crd_gate_reverse(self):
+        "Test reverse cross-repo dependencies"
+        A = self.fake_gerrit.addFakeChange('gerrit/project1', 'master', 'A')
+        B = self.fake_github.openFakePullRequest('github/project2', 'master',
+                                                 'B')
+        A.addApproval('Code-Review', 2)
+
+        # A Depends-On: B
+
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.url)
+
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertFalse(B.is_merged)
+
+        self.executor_server.hold_jobs_in_build = True
+        A.addApproval('Approved', 1)
+        self.fake_github.emitEvent(B.addLabel('approved'))
+        self.waitUntilSettled()
+
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'MERGED')
+        self.assertTrue(B.is_merged)
+        self.assertEqual(A.reported, 2)
+        self.assertEqual(len(B.comments), 2)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'gerrit/project1').changes
+        self.assertEqual(changes, '1,%s 1,1' %
+                         (B.head_sha,))
+
+    def test_crd_cycle(self):
+        "Test cross-repo dependency cycles"
+        A = self.fake_gerrit.addFakeChange('gerrit/project1', 'master', 'A')
+        msg = "Depends-On: %s" % (A.data['url'],)
+        B = self.fake_github.openFakePullRequest('github/project2', 'master',
+                                                 'B', body=msg)
+        A.addApproval('Code-Review', 2)
+        B.addLabel('approved')
+
+        # A -> B -> A (via commit-depends)
+
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.url)
+
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.reported, 0)
+        self.assertEqual(len(B.comments), 0)
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertFalse(B.is_merged)
+
+    def test_crd_gate_unknown(self):
+        "Test unknown projects in dependent pipeline"
+        self.init_repo("github/unknown", tag='init')
+        A = self.fake_gerrit.addFakeChange('gerrit/project1', 'master', 'A')
+        B = self.fake_github.openFakePullRequest('github/unknown', 'master',
+                                                 'B')
+        A.addApproval('Code-Review', 2)
+
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.url)
+
+        event = B.addLabel('approved')
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        # Unknown projects cannot share a queue with any other
+        # since they don't have common jobs with any other (they have no jobs).
+        # Changes which depend on unknown project changes
+        # should not be processed in dependent pipeline
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertFalse(B.is_merged)
+        self.assertEqual(A.reported, 0)
+        self.assertEqual(len(B.comments), 0)
+        self.assertEqual(len(self.history), 0)
+
+        # Simulate change B being gated outside this layout Set the
+        # change merged before submitting the event so that when the
+        # event triggers a gerrit query to update the change, we get
+        # the information that it was merged.
+        B.setMerged('merged')
+        self.fake_github.emitEvent(event)
+        self.waitUntilSettled()
+        self.assertEqual(len(self.history), 0)
+
+        # Now that B is merged, A should be able to be enqueued and
+        # merged.
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'MERGED')
+        self.assertEqual(A.reported, 2)
+        self.assertTrue(B.is_merged)
+        self.assertEqual(len(B.comments), 0)
+
+    def test_crd_check(self):
+        "Test cross-repo dependencies in independent pipelines"
+        self.executor_server.hold_jobs_in_build = True
+        self.gearman_server.hold_jobs_in_queue = True
+        A = self.fake_gerrit.addFakeChange('gerrit/project1', 'master', 'A')
+        B = self.fake_github.openFakePullRequest(
+            'github/project2', 'master', 'B')
+
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.url)
+
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        self.gearman_server.hold_jobs_in_queue = False
+        self.gearman_server.release()
+        self.waitUntilSettled()
+
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+
+        self.assertTrue(self.builds[0].hasChanges(A, B))
+
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertFalse(B.is_merged)
+        self.assertEqual(A.reported, 1)
+        self.assertEqual(len(B.comments), 0)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'gerrit/project1').changes
+        self.assertEqual(changes, '1,%s 1,1' %
+                         (B.head_sha,))
+
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 0)
+
+    def test_crd_check_duplicate(self):
+        "Test duplicate check in independent pipelines"
+        self.executor_server.hold_jobs_in_build = True
+        A = self.fake_gerrit.addFakeChange('gerrit/project1', 'master', 'A')
+        B = self.fake_github.openFakePullRequest(
+            'github/project2', 'master', 'B')
+
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.url)
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        check_pipeline = tenant.layout.pipelines['check']
+
+        # Add two dependent changes...
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(len(check_pipeline.getAllItems()), 2)
+
+        # ...make sure the live one is not duplicated...
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(len(check_pipeline.getAllItems()), 2)
+
+        # ...but the non-live one is able to be.
+        self.fake_github.emitEvent(B.getPullRequestEditedEvent())
+        self.waitUntilSettled()
+        self.assertEqual(len(check_pipeline.getAllItems()), 3)
+
+        # Release jobs in order to avoid races with change A jobs
+        # finishing before change B jobs.
+        self.orderedRelease()
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertFalse(B.is_merged)
+        self.assertEqual(A.reported, 1)
+        self.assertEqual(len(B.comments), 1)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'gerrit/project1').changes
+        self.assertEqual(changes, '1,%s 1,1' %
+                         (B.head_sha,))
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'github/project2').changes
+        self.assertEqual(changes, '1,%s' %
+                         (B.head_sha,))
+        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 0)
+
+        self.assertIn('Build succeeded', A.messages[0])
+
+    def _test_crd_check_reconfiguration(self, project1, project2):
+        "Test cross-repo dependencies re-enqueued in independent pipelines"
+
+        self.gearman_server.hold_jobs_in_queue = True
+        A = self.fake_gerrit.addFakeChange('gerrit/project1', 'master', 'A')
+        B = self.fake_github.openFakePullRequest(
+            'github/project2', 'master', 'B')
+
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.url)
+
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        self.sched.reconfigure(self.config)
+
+        # Make sure the items still share a change queue, and the
+        # first one is not live.
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 1)
+        queue = tenant.layout.pipelines['check'].queues[0]
+        first_item = queue.queue[0]
+        for item in queue.queue:
+            self.assertEqual(item.queue, first_item.queue)
+        self.assertFalse(first_item.live)
+        self.assertTrue(queue.queue[1].live)
+
+        self.gearman_server.hold_jobs_in_queue = False
+        self.gearman_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertFalse(B.is_merged)
+        self.assertEqual(A.reported, 1)
+        self.assertEqual(len(B.comments), 0)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'gerrit/project1').changes
+        self.assertEqual(changes, '1,%s 1,1' %
+                         (B.head_sha,))
+        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 0)
+
+    def test_crd_check_reconfiguration(self):
+        self._test_crd_check_reconfiguration('org/project1', 'org/project2')
+
+    def test_crd_undefined_project(self):
+        """Test that undefined projects in dependencies are handled for
+        independent pipelines"""
+        # It's a hack for fake github,
+        # as it implies repo creation upon the creation of any change
+        self.init_repo("github/unknown", tag='init')
+        self._test_crd_check_reconfiguration('gerrit/project1',
+                                             'github/unknown')
+
+    def test_crd_check_transitive(self):
+        "Test transitive cross-repo dependencies"
+        # Specifically, if A -> B -> C, and C gets a new patchset and
+        # A gets a new patchset, ensure the test of A,2 includes B,1
+        # and C,2 (not C,1 which would indicate stale data in the
+        # cache for B).
+        A = self.fake_gerrit.addFakeChange('gerrit/project1', 'master', 'A')
+        C = self.fake_gerrit.addFakeChange('gerrit/project1', 'master', 'C')
+        # B Depends-On: C
+        msg = "Depends-On: %s" % (C.data['url'],)
+        B = self.fake_github.openFakePullRequest(
+            'github/project2', 'master', 'B', body=msg)
+
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.url)
+
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '2,1 1,%s 1,1' %
+                         (B.head_sha,))
+
+        self.fake_github.emitEvent(B.getPullRequestEditedEvent())
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '2,1 1,%s' %
+                         (B.head_sha,))
+
+        self.fake_gerrit.addEvent(C.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '2,1')
+
+        C.addPatchset()
+        self.fake_gerrit.addEvent(C.getPatchsetCreatedEvent(2))
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '2,2')
+
+        A.addPatchset()
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(2))
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '2,2 1,%s 1,2' %
+                         (B.head_sha,))
+
+    def test_crd_check_unknown(self):
+        "Test unknown projects in independent pipeline"
+        self.init_repo("github/unknown", tag='init')
+        A = self.fake_gerrit.addFakeChange('gerrit/project1', 'master', 'A')
+        B = self.fake_github.openFakePullRequest(
+            'github/unknown', 'master', 'B')
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.url)
+
+        # Make sure zuul has seen an event on B.
+        self.fake_github.emitEvent(B.getPullRequestEditedEvent())
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(A.reported, 1)
+        self.assertFalse(B.is_merged)
+        self.assertEqual(len(B.comments), 0)
+
+    def test_crd_cycle_join(self):
+        "Test an updated change creates a cycle"
+        A = self.fake_github.openFakePullRequest(
+            'github/project2', 'master', 'A')
+
+        self.fake_github.emitEvent(A.getPullRequestEditedEvent())
+        self.waitUntilSettled()
+        self.assertEqual(len(A.comments), 1)
+
+        # Create B->A
+        B = self.fake_gerrit.addFakeChange('gerrit/project1', 'master', 'B')
+        B.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            B.subject, A.url)
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        # Dep is there so zuul should have reported on B
+        self.assertEqual(B.reported, 1)
+
+        # Update A to add A->B (a cycle).
+        A.editBody('Depends-On: %s\n' % (B.data['url']))
+        self.fake_github.emitEvent(A.getPullRequestEditedEvent())
+        self.waitUntilSettled()
+
+        # Dependency cycle injected so zuul should not have reported again on A
+        self.assertEqual(len(A.comments), 1)
+
+        # Now if we update B to remove the depends-on, everything
+        # should be okay.  B; A->B
+
+        B.addPatchset()
+        B.data['commitMessage'] = '%s\n' % (B.subject,)
+        self.fake_github.emitEvent(A.getPullRequestEditedEvent())
+        self.waitUntilSettled()
+
+        # Cycle was removed so now zuul should have reported again on A
+        self.assertEqual(len(A.comments), 2)
+
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(2))
+        self.waitUntilSettled()
+        self.assertEqual(B.reported, 2)
+
+
+class TestGithubToGerritCRD(ZuulTestCase):
+    config_file = 'zuul-gerrit-github.conf'
+    tenant_config_file = 'config/cross-source/main.yaml'
+
+    def test_crd_gate(self):
+        "Test cross-repo dependencies"
+        A = self.fake_github.openFakePullRequest('github/project2', 'master',
+                                                 'A')
+        B = self.fake_gerrit.addFakeChange('gerrit/project1', 'master', 'B')
+
+        B.addApproval('Code-Review', 2)
+
+        # A Depends-On: B
+        A.editBody('Depends-On: %s\n' % (B.data['url']))
+
+        event = A.addLabel('approved')
+        self.fake_github.emitEvent(event)
+        self.waitUntilSettled()
+
+        self.assertFalse(A.is_merged)
+        self.assertEqual(B.data['status'], 'NEW')
+
+        for connection in self.connections.connections.values():
+            connection.maintainCache([])
+
+        self.executor_server.hold_jobs_in_build = True
+        B.addApproval('Approved', 1)
+        self.fake_github.emitEvent(event)
+        self.waitUntilSettled()
+
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertTrue(A.is_merged)
+        self.assertEqual(B.data['status'], 'MERGED')
+        self.assertEqual(len(A.comments), 2)
+        self.assertEqual(B.reported, 2)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'github/project2').changes
+        self.assertEqual(changes, '1,1 1,%s' % A.head_sha)
+
+    def test_crd_branch(self):
+        "Test cross-repo dependencies in multiple branches"
+
+        self.create_branch('gerrit/project1', 'mp')
+        A = self.fake_github.openFakePullRequest('github/project2', 'master',
+                                                 'A')
+        B = self.fake_gerrit.addFakeChange('gerrit/project1', 'master', 'B')
+        C1 = self.fake_gerrit.addFakeChange('gerrit/project1', 'mp', 'C1')
+
+        B.addApproval('Code-Review', 2)
+        C1.addApproval('Code-Review', 2)
+
+        # A Depends-On: B+C1
+        A.editBody('Depends-On: %s\nDepends-On: %s\n' % (
+            B.data['url'], C1.data['url']))
+
+        self.executor_server.hold_jobs_in_build = True
+        B.addApproval('Approved', 1)
+        C1.addApproval('Approved', 1)
+        self.fake_github.emitEvent(A.addLabel('approved'))
+        self.waitUntilSettled()
+
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+        self.assertTrue(A.is_merged)
+        self.assertEqual(B.data['status'], 'MERGED')
+        self.assertEqual(C1.data['status'], 'MERGED')
+        self.assertEqual(len(A.comments), 2)
+        self.assertEqual(B.reported, 2)
+        self.assertEqual(C1.reported, 2)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'github/project2').changes
+        self.assertEqual(changes, '1,1 2,1 1,%s' %
+                         (A.head_sha,))
+
+    def test_crd_gate_reverse(self):
+        "Test reverse cross-repo dependencies"
+        A = self.fake_github.openFakePullRequest('github/project2', 'master',
+                                                 'A')
+        B = self.fake_gerrit.addFakeChange('gerrit/project1', 'master', 'B')
+        B.addApproval('Code-Review', 2)
+
+        # A Depends-On: B
+        A.editBody('Depends-On: %s\n' % (B.data['url'],))
+
+        self.fake_github.emitEvent(A.addLabel('approved'))
+        self.waitUntilSettled()
+
+        self.assertFalse(A.is_merged)
+        self.assertEqual(B.data['status'], 'NEW')
+
+        self.executor_server.hold_jobs_in_build = True
+        A.addLabel('approved')
+        self.fake_gerrit.addEvent(B.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertTrue(A.is_merged)
+        self.assertEqual(B.data['status'], 'MERGED')
+        self.assertEqual(len(A.comments), 2)
+        self.assertEqual(B.reported, 2)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'github/project2').changes
+        self.assertEqual(changes, '1,1 1,%s' %
+                         (A.head_sha,))
+
+    def test_crd_cycle(self):
+        "Test cross-repo dependency cycles"
+        A = self.fake_github.openFakePullRequest('github/project2', 'master',
+                                                 'A')
+        B = self.fake_gerrit.addFakeChange('gerrit/project1', 'master', 'B')
+        B.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            B.subject, A.url)
+
+        B.addApproval('Code-Review', 2)
+        B.addApproval('Approved', 1)
+
+        # A -> B -> A (via commit-depends)
+        A.editBody('Depends-On: %s\n' % (B.data['url'],))
+
+        self.fake_github.emitEvent(A.addLabel('approved'))
+        self.waitUntilSettled()
+
+        self.assertEqual(len(A.comments), 0)
+        self.assertEqual(B.reported, 0)
+        self.assertFalse(A.is_merged)
+        self.assertEqual(B.data['status'], 'NEW')
+
+    def test_crd_gate_unknown(self):
+        "Test unknown projects in dependent pipeline"
+        self.init_repo("gerrit/unknown", tag='init')
+        A = self.fake_github.openFakePullRequest('github/project2', 'master',
+                                                 'A')
+        B = self.fake_gerrit.addFakeChange('gerrit/unknown', 'master', 'B')
+        B.addApproval('Code-Review', 2)
+
+        # A Depends-On: B
+        A.editBody('Depends-On: %s\n' % (B.data['url'],))
+
+        B.addApproval('Approved', 1)
+        event = A.addLabel('approved')
+        self.fake_github.emitEvent(event)
+        self.waitUntilSettled()
+
+        # Unknown projects cannot share a queue with any other
+        # since they don't have common jobs with any other (they have no jobs).
+        # Changes which depend on unknown project changes
+        # should not be processed in dependent pipeline
+        self.assertFalse(A.is_merged)
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(len(A.comments), 0)
+        self.assertEqual(B.reported, 0)
+        self.assertEqual(len(self.history), 0)
+
+        # Simulate change B being gated outside this layout Set the
+        # change merged before submitting the event so that when the
+        # event triggers a gerrit query to update the change, we get
+        # the information that it was merged.
+        B.setMerged()
+        self.fake_gerrit.addEvent(B.addApproval('Approved', 1))
+        self.waitUntilSettled()
+        self.assertEqual(len(self.history), 0)
+
+        # Now that B is merged, A should be able to be enqueued and
+        # merged.
+        self.fake_github.emitEvent(event)
+        self.waitUntilSettled()
+
+        self.assertTrue(A.is_merged)
+        self.assertEqual(len(A.comments), 2)
+        self.assertEqual(B.data['status'], 'MERGED')
+        self.assertEqual(B.reported, 0)
+
+    def test_crd_check(self):
+        "Test cross-repo dependencies in independent pipelines"
+        self.executor_server.hold_jobs_in_build = True
+        self.gearman_server.hold_jobs_in_queue = True
+        A = self.fake_github.openFakePullRequest('github/project2', 'master',
+                                                 'A')
+        B = self.fake_gerrit.addFakeChange(
+            'gerrit/project1', 'master', 'B')
+
+        # A Depends-On: B
+        A.editBody('Depends-On: %s\n' % (B.data['url'],))
+
+        self.fake_github.emitEvent(A.getPullRequestEditedEvent())
+        self.waitUntilSettled()
+
+        self.gearman_server.hold_jobs_in_queue = False
+        self.gearman_server.release()
+        self.waitUntilSettled()
+
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+
+        self.assertTrue(self.builds[0].hasChanges(A, B))
+
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertFalse(A.is_merged)
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(len(A.comments), 1)
+        self.assertEqual(B.reported, 0)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'github/project2').changes
+        self.assertEqual(changes, '1,1 1,%s' %
+                         (A.head_sha,))
+
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 0)
+
+    def test_crd_check_duplicate(self):
+        "Test duplicate check in independent pipelines"
+        self.executor_server.hold_jobs_in_build = True
+        A = self.fake_github.openFakePullRequest('github/project2', 'master',
+                                                 'A')
+        B = self.fake_gerrit.addFakeChange(
+            'gerrit/project1', 'master', 'B')
+
+        # A Depends-On: B
+        A.editBody('Depends-On: %s\n' % (B.data['url'],))
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        check_pipeline = tenant.layout.pipelines['check']
+
+        # Add two dependent changes...
+        self.fake_github.emitEvent(A.getPullRequestEditedEvent())
+        self.waitUntilSettled()
+        self.assertEqual(len(check_pipeline.getAllItems()), 2)
+
+        # ...make sure the live one is not duplicated...
+        self.fake_github.emitEvent(A.getPullRequestEditedEvent())
+        self.waitUntilSettled()
+        self.assertEqual(len(check_pipeline.getAllItems()), 2)
+
+        # ...but the non-live one is able to be.
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(len(check_pipeline.getAllItems()), 3)
+
+        # Release jobs in order to avoid races with change A jobs
+        # finishing before change B jobs.
+        self.orderedRelease()
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertFalse(A.is_merged)
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(len(A.comments), 1)
+        self.assertEqual(B.reported, 1)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'github/project2').changes
+        self.assertEqual(changes, '1,1 1,%s' %
+                         (A.head_sha,))
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'gerrit/project1').changes
+        self.assertEqual(changes, '1,1')
+        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 0)
+
+        self.assertIn('Build succeeded', A.comments[0])
+
+    def _test_crd_check_reconfiguration(self, project1, project2):
+        "Test cross-repo dependencies re-enqueued in independent pipelines"
+
+        self.gearman_server.hold_jobs_in_queue = True
+        A = self.fake_github.openFakePullRequest('github/project2', 'master',
+                                                 'A')
+        B = self.fake_gerrit.addFakeChange(
+            'gerrit/project1', 'master', 'B')
+
+        # A Depends-On: B
+        A.editBody('Depends-On: %s\n' % (B.data['url'],))
+
+        self.fake_github.emitEvent(A.getPullRequestEditedEvent())
+        self.waitUntilSettled()
+
+        self.sched.reconfigure(self.config)
+
+        # Make sure the items still share a change queue, and the
+        # first one is not live.
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 1)
+        queue = tenant.layout.pipelines['check'].queues[0]
+        first_item = queue.queue[0]
+        for item in queue.queue:
+            self.assertEqual(item.queue, first_item.queue)
+        self.assertFalse(first_item.live)
+        self.assertTrue(queue.queue[1].live)
+
+        self.gearman_server.hold_jobs_in_queue = False
+        self.gearman_server.release()
+        self.waitUntilSettled()
+
+        self.assertFalse(A.is_merged)
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(len(A.comments), 1)
+        self.assertEqual(B.reported, 0)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'github/project2').changes
+        self.assertEqual(changes, '1,1 1,%s' %
+                         (A.head_sha,))
+        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 0)
+
+    def test_crd_check_reconfiguration(self):
+        self._test_crd_check_reconfiguration('org/project1', 'org/project2')
+
+    def test_crd_undefined_project(self):
+        """Test that undefined projects in dependencies are handled for
+        independent pipelines"""
+        # It's a hack for fake gerrit,
+        # as it implies repo creation upon the creation of any change
+        self.init_repo("gerrit/unknown", tag='init')
+        self._test_crd_check_reconfiguration('github/project2',
+                                             'gerrit/unknown')
+
+    def test_crd_check_transitive(self):
+        "Test transitive cross-repo dependencies"
+        # Specifically, if A -> B -> C, and C gets a new patchset and
+        # A gets a new patchset, ensure the test of A,2 includes B,1
+        # and C,2 (not C,1 which would indicate stale data in the
+        # cache for B).
+        A = self.fake_github.openFakePullRequest('github/project2', 'master',
+                                                 'A')
+        B = self.fake_gerrit.addFakeChange('gerrit/project1', 'master', 'B')
+        C = self.fake_github.openFakePullRequest('github/project2', 'master',
+                                                 'C')
+
+        # B Depends-On: C
+        B.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            B.subject, C.url)
+
+        # A Depends-On: B
+        A.editBody('Depends-On: %s\n' % (B.data['url'],))
+
+        self.fake_github.emitEvent(A.getPullRequestEditedEvent())
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '2,%s 1,1 1,%s' %
+                         (C.head_sha, A.head_sha))
+
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '2,%s 1,1' %
+                         (C.head_sha,))
+
+        self.fake_github.emitEvent(C.getPullRequestEditedEvent())
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '2,%s' %
+                         (C.head_sha,))
+
+        new_c_head = C.head_sha
+        C.addCommit()
+        old_c_head = C.head_sha
+        self.assertNotEqual(old_c_head, new_c_head)
+        self.fake_github.emitEvent(C.getPullRequestEditedEvent())
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '2,%s' %
+                         (C.head_sha,))
+
+        new_a_head = A.head_sha
+        A.addCommit()
+        old_a_head = A.head_sha
+        self.assertNotEqual(old_a_head, new_a_head)
+        self.fake_github.emitEvent(A.getPullRequestEditedEvent())
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '2,%s 1,1 1,%s' %
+                         (C.head_sha, A.head_sha,))
+
+    def test_crd_check_unknown(self):
+        "Test unknown projects in independent pipeline"
+        self.init_repo("gerrit/unknown", tag='init')
+        A = self.fake_github.openFakePullRequest('github/project2', 'master',
+                                                 'A')
+        B = self.fake_gerrit.addFakeChange(
+            'gerrit/unknown', 'master', 'B')
+
+        # A Depends-On: B
+        A.editBody('Depends-On: %s\n' % (B.data['url'],))
+
+        # Make sure zuul has seen an event on B.
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+        self.fake_github.emitEvent(A.getPullRequestEditedEvent())
+        self.waitUntilSettled()
+
+        self.assertFalse(A.is_merged)
+        self.assertEqual(len(A.comments), 1)
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(B.reported, 0)
+
+    def test_crd_cycle_join(self):
+        "Test an updated change creates a cycle"
+        A = self.fake_gerrit.addFakeChange(
+            'gerrit/project1', 'master', 'A')
+
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(A.reported, 1)
+
+        # Create B->A
+        B = self.fake_github.openFakePullRequest('github/project2', 'master',
+                                                 'B')
+        B.editBody('Depends-On: %s\n' % (A.data['url'],))
+        self.fake_github.emitEvent(B.getPullRequestEditedEvent())
+        self.waitUntilSettled()
+
+        # Dep is there so zuul should have reported on B
+        self.assertEqual(len(B.comments), 1)
+
+        # Update A to add A->B (a cycle).
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.url)
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        # Dependency cycle injected so zuul should not have reported again on A
+        self.assertEqual(A.reported, 1)
+
+        # Now if we update B to remove the depends-on, everything
+        # should be okay.  B; A->B
+
+        B.addCommit()
+        B.editBody('')
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        # Cycle was removed so now zuul should have reported again on A
+        self.assertEqual(A.reported, 2)
+
+        self.fake_github.emitEvent(B.getPullRequestEditedEvent())
+        self.waitUntilSettled()
+        self.assertEqual(len(B.comments), 2)
diff --git a/tests/unit/test_gerrit_crd.py b/tests/unit/test_gerrit_crd.py
new file mode 100644
index 0000000..732bc3d
--- /dev/null
+++ b/tests/unit/test_gerrit_crd.py
@@ -0,0 +1,626 @@
+#!/usr/bin/env python
+
+# Copyright 2012 Hewlett-Packard Development Company, L.P.
+# Copyright 2018 Red Hat, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+from tests.base import (
+    ZuulTestCase,
+    simple_layout,
+)
+
+
+class TestGerritCRD(ZuulTestCase):
+    tenant_config_file = 'config/single-tenant/main.yaml'
+
+    def test_crd_gate(self):
+        "Test cross-repo dependencies"
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
+        A.addApproval('Code-Review', 2)
+        B.addApproval('Code-Review', 2)
+
+        AM2 = self.fake_gerrit.addFakeChange('org/project1', 'master', 'AM2')
+        AM1 = self.fake_gerrit.addFakeChange('org/project1', 'master', 'AM1')
+        AM2.setMerged()
+        AM1.setMerged()
+
+        BM2 = self.fake_gerrit.addFakeChange('org/project2', 'master', 'BM2')
+        BM1 = self.fake_gerrit.addFakeChange('org/project2', 'master', 'BM1')
+        BM2.setMerged()
+        BM1.setMerged()
+
+        # A -> AM1 -> AM2
+        # B -> BM1 -> BM2
+        # A Depends-On: B
+        # M2 is here to make sure it is never queried.  If it is, it
+        # means zuul is walking down the entire history of merged
+        # changes.
+
+        B.setDependsOn(BM1, 1)
+        BM1.setDependsOn(BM2, 1)
+
+        A.setDependsOn(AM1, 1)
+        AM1.setDependsOn(AM2, 1)
+
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['url'])
+
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+
+        for connection in self.connections.connections.values():
+            connection.maintainCache([])
+
+        self.executor_server.hold_jobs_in_build = True
+        B.addApproval('Approved', 1)
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(AM2.queried, 0)
+        self.assertEqual(BM2.queried, 0)
+        self.assertEqual(A.data['status'], 'MERGED')
+        self.assertEqual(B.data['status'], 'MERGED')
+        self.assertEqual(A.reported, 2)
+        self.assertEqual(B.reported, 2)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'org/project1').changes
+        self.assertEqual(changes, '2,1 1,1')
+
+    def test_crd_branch(self):
+        "Test cross-repo dependencies in multiple branches"
+
+        self.create_branch('org/project2', 'mp')
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
+        C1 = self.fake_gerrit.addFakeChange('org/project2', 'mp', 'C1')
+
+        A.addApproval('Code-Review', 2)
+        B.addApproval('Code-Review', 2)
+        C1.addApproval('Code-Review', 2)
+
+        # A Depends-On: B+C1
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\nDepends-On: %s\n' % (
+            A.subject, B.data['url'], C1.data['url'])
+
+        self.executor_server.hold_jobs_in_build = True
+        B.addApproval('Approved', 1)
+        C1.addApproval('Approved', 1)
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'MERGED')
+        self.assertEqual(B.data['status'], 'MERGED')
+        self.assertEqual(C1.data['status'], 'MERGED')
+        self.assertEqual(A.reported, 2)
+        self.assertEqual(B.reported, 2)
+        self.assertEqual(C1.reported, 2)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'org/project1').changes
+        self.assertEqual(changes, '2,1 3,1 1,1')
+
+    def test_crd_multiline(self):
+        "Test multiple depends-on lines in commit"
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
+        C = self.fake_gerrit.addFakeChange('org/project2', 'master', 'C')
+        A.addApproval('Code-Review', 2)
+        B.addApproval('Code-Review', 2)
+        C.addApproval('Code-Review', 2)
+
+        # A Depends-On: B+C
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\nDepends-On: %s\n' % (
+            A.subject, B.data['url'], C.data['url'])
+
+        self.executor_server.hold_jobs_in_build = True
+        B.addApproval('Approved', 1)
+        C.addApproval('Approved', 1)
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'MERGED')
+        self.assertEqual(B.data['status'], 'MERGED')
+        self.assertEqual(C.data['status'], 'MERGED')
+        self.assertEqual(A.reported, 2)
+        self.assertEqual(B.reported, 2)
+        self.assertEqual(C.reported, 2)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'org/project1').changes
+        self.assertEqual(changes, '2,1 3,1 1,1')
+
+    def test_crd_unshared_gate(self):
+        "Test cross-repo dependencies in unshared gate queues"
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project', 'master', 'B')
+        A.addApproval('Code-Review', 2)
+        B.addApproval('Code-Review', 2)
+
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['url'])
+
+        # A and B do not share a queue, make sure that A is unable to
+        # enqueue B (and therefore, A is unable to be enqueued).
+        B.addApproval('Approved', 1)
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(A.reported, 0)
+        self.assertEqual(B.reported, 0)
+        self.assertEqual(len(self.history), 0)
+
+        # Enqueue and merge B alone.
+        self.fake_gerrit.addEvent(B.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(B.data['status'], 'MERGED')
+        self.assertEqual(B.reported, 2)
+
+        # Now that B is merged, A should be able to be enqueued and
+        # merged.
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'MERGED')
+        self.assertEqual(A.reported, 2)
+
+    def test_crd_gate_reverse(self):
+        "Test reverse cross-repo dependencies"
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
+        A.addApproval('Code-Review', 2)
+        B.addApproval('Code-Review', 2)
+
+        # A Depends-On: B
+
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['url'])
+
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+
+        self.executor_server.hold_jobs_in_build = True
+        A.addApproval('Approved', 1)
+        self.fake_gerrit.addEvent(B.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'MERGED')
+        self.assertEqual(B.data['status'], 'MERGED')
+        self.assertEqual(A.reported, 2)
+        self.assertEqual(B.reported, 2)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'org/project1').changes
+        self.assertEqual(changes, '2,1 1,1')
+
+    def test_crd_cycle(self):
+        "Test cross-repo dependency cycles"
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
+        A.addApproval('Code-Review', 2)
+        B.addApproval('Code-Review', 2)
+
+        # A -> B -> A (via commit-depends)
+
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['url'])
+        B.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            B.subject, A.data['url'])
+
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.reported, 0)
+        self.assertEqual(B.reported, 0)
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+
+    def test_crd_gate_unknown(self):
+        "Test unknown projects in dependent pipeline"
+        self.init_repo("org/unknown", tag='init')
+        A = self.fake_gerrit.addFakeChange('org/project', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/unknown', 'master', 'B')
+        A.addApproval('Code-Review', 2)
+        B.addApproval('Code-Review', 2)
+
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['url'])
+
+        B.addApproval('Approved', 1)
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        # Unknown projects cannot share a queue with any other
+        # since they don't have common jobs with any other (they have no jobs).
+        # Changes which depend on unknown project changes
+        # should not be processed in dependent pipeline
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(A.reported, 0)
+        self.assertEqual(B.reported, 0)
+        self.assertEqual(len(self.history), 0)
+
+        # Simulate change B being gated outside this layout Set the
+        # change merged before submitting the event so that when the
+        # event triggers a gerrit query to update the change, we get
+        # the information that it was merged.
+        B.setMerged()
+        self.fake_gerrit.addEvent(B.addApproval('Approved', 1))
+        self.waitUntilSettled()
+        self.assertEqual(len(self.history), 0)
+
+        # Now that B is merged, A should be able to be enqueued and
+        # merged.
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'MERGED')
+        self.assertEqual(A.reported, 2)
+        self.assertEqual(B.data['status'], 'MERGED')
+        self.assertEqual(B.reported, 0)
+
+    def test_crd_check(self):
+        "Test cross-repo dependencies in independent pipelines"
+
+        self.executor_server.hold_jobs_in_build = True
+        self.gearman_server.hold_jobs_in_queue = True
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
+
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['url'])
+
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        self.gearman_server.hold_jobs_in_queue = False
+        self.gearman_server.release()
+        self.waitUntilSettled()
+
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+
+        self.assertTrue(self.builds[0].hasChanges(A, B))
+
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(A.reported, 1)
+        self.assertEqual(B.reported, 0)
+
+        self.assertEqual(self.history[0].changes, '2,1 1,1')
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 0)
+
+    def test_crd_check_git_depends(self):
+        "Test single-repo dependencies in independent pipelines"
+        self.gearman_server.hold_jobs_in_build = True
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project1', 'master', 'B')
+
+        # Add two git-dependent changes and make sure they both report
+        # success.
+        B.setDependsOn(A, 1)
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        self.orderedRelease()
+        self.gearman_server.hold_jobs_in_build = False
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(A.reported, 1)
+        self.assertEqual(B.reported, 1)
+
+        self.assertEqual(self.history[0].changes, '1,1')
+        self.assertEqual(self.history[-1].changes, '1,1 2,1')
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 0)
+
+        self.assertIn('Build succeeded', A.messages[0])
+        self.assertIn('Build succeeded', B.messages[0])
+
+    def test_crd_check_duplicate(self):
+        "Test duplicate check in independent pipelines"
+        self.executor_server.hold_jobs_in_build = True
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project1', 'master', 'B')
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        check_pipeline = tenant.layout.pipelines['check']
+
+        # Add two git-dependent changes...
+        B.setDependsOn(A, 1)
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(len(check_pipeline.getAllItems()), 2)
+
+        # ...make sure the live one is not duplicated...
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(len(check_pipeline.getAllItems()), 2)
+
+        # ...but the non-live one is able to be.
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(len(check_pipeline.getAllItems()), 3)
+
+        # Release jobs in order to avoid races with change A jobs
+        # finishing before change B jobs.
+        self.orderedRelease()
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(A.reported, 1)
+        self.assertEqual(B.reported, 1)
+
+        self.assertEqual(self.history[0].changes, '1,1 2,1')
+        self.assertEqual(self.history[1].changes, '1,1')
+        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 0)
+
+        self.assertIn('Build succeeded', A.messages[0])
+        self.assertIn('Build succeeded', B.messages[0])
+
+    def _test_crd_check_reconfiguration(self, project1, project2):
+        "Test cross-repo dependencies re-enqueued in independent pipelines"
+
+        self.gearman_server.hold_jobs_in_queue = True
+        A = self.fake_gerrit.addFakeChange(project1, 'master', 'A')
+        B = self.fake_gerrit.addFakeChange(project2, 'master', 'B')
+
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['url'])
+
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        self.sched.reconfigure(self.config)
+
+        # Make sure the items still share a change queue, and the
+        # first one is not live.
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 1)
+        queue = tenant.layout.pipelines['check'].queues[0]
+        first_item = queue.queue[0]
+        for item in queue.queue:
+            self.assertEqual(item.queue, first_item.queue)
+        self.assertFalse(first_item.live)
+        self.assertTrue(queue.queue[1].live)
+
+        self.gearman_server.hold_jobs_in_queue = False
+        self.gearman_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(A.reported, 1)
+        self.assertEqual(B.reported, 0)
+
+        self.assertEqual(self.history[0].changes, '2,1 1,1')
+        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 0)
+
+    def test_crd_check_reconfiguration(self):
+        self._test_crd_check_reconfiguration('org/project1', 'org/project2')
+
+    def test_crd_undefined_project(self):
+        """Test that undefined projects in dependencies are handled for
+        independent pipelines"""
+        # It's a hack for fake gerrit,
+        # as it implies repo creation upon the creation of any change
+        self.init_repo("org/unknown", tag='init')
+        self._test_crd_check_reconfiguration('org/project1', 'org/unknown')
+
+    @simple_layout('layouts/ignore-dependencies.yaml')
+    def test_crd_check_ignore_dependencies(self):
+        "Test cross-repo dependencies can be ignored"
+
+        self.gearman_server.hold_jobs_in_queue = True
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
+        C = self.fake_gerrit.addFakeChange('org/project2', 'master', 'C')
+
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['url'])
+        # C git-depends on B
+        C.setDependsOn(B, 1)
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+        self.fake_gerrit.addEvent(C.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        # Make sure none of the items share a change queue, and all
+        # are live.
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        check_pipeline = tenant.layout.pipelines['check']
+        self.assertEqual(len(check_pipeline.queues), 3)
+        self.assertEqual(len(check_pipeline.getAllItems()), 3)
+        for item in check_pipeline.getAllItems():
+            self.assertTrue(item.live)
+
+        self.gearman_server.hold_jobs_in_queue = False
+        self.gearman_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(C.data['status'], 'NEW')
+        self.assertEqual(A.reported, 1)
+        self.assertEqual(B.reported, 1)
+        self.assertEqual(C.reported, 1)
+
+        # Each job should have tested exactly one change
+        for job in self.history:
+            self.assertEqual(len(job.changes.split()), 1)
+
+    @simple_layout('layouts/three-projects.yaml')
+    def test_crd_check_transitive(self):
+        "Test transitive cross-repo dependencies"
+        # Specifically, if A -> B -> C, and C gets a new patchset and
+        # A gets a new patchset, ensure the test of A,2 includes B,1
+        # and C,2 (not C,1 which would indicate stale data in the
+        # cache for B).
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
+        C = self.fake_gerrit.addFakeChange('org/project3', 'master', 'C')
+
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['url'])
+
+        # B Depends-On: C
+        B.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            B.subject, C.data['url'])
+
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '3,1 2,1 1,1')
+
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '3,1 2,1')
+
+        self.fake_gerrit.addEvent(C.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '3,1')
+
+        C.addPatchset()
+        self.fake_gerrit.addEvent(C.getPatchsetCreatedEvent(2))
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '3,2')
+
+        A.addPatchset()
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(2))
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '3,2 2,1 1,2')
+
+    def test_crd_check_unknown(self):
+        "Test unknown projects in independent pipeline"
+        self.init_repo("org/unknown", tag='init')
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/unknown', 'master', 'D')
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['url'])
+
+        # Make sure zuul has seen an event on B.
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(A.reported, 1)
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(B.reported, 0)
+
+    def test_crd_cycle_join(self):
+        "Test an updated change creates a cycle"
+        A = self.fake_gerrit.addFakeChange('org/project2', 'master', 'A')
+
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(A.reported, 1)
+
+        # Create B->A
+        B = self.fake_gerrit.addFakeChange('org/project1', 'master', 'B')
+        B.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            B.subject, A.data['url'])
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        # Dep is there so zuul should have reported on B
+        self.assertEqual(B.reported, 1)
+
+        # Update A to add A->B (a cycle).
+        A.addPatchset()
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['url'])
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(2))
+        self.waitUntilSettled()
+
+        # Dependency cycle injected so zuul should not have reported again on A
+        self.assertEqual(A.reported, 1)
+
+        # Now if we update B to remove the depends-on, everything
+        # should be okay.  B; A->B
+
+        B.addPatchset()
+        B.data['commitMessage'] = '%s\n' % (B.subject,)
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(2))
+        self.waitUntilSettled()
+
+        # Cycle was removed so now zuul should have reported again on A
+        self.assertEqual(A.reported, 2)
+
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(2))
+        self.waitUntilSettled()
+        self.assertEqual(B.reported, 2)
diff --git a/tests/unit/test_gerrit_legacy_crd.py b/tests/unit/test_gerrit_legacy_crd.py
new file mode 100644
index 0000000..c711e4d
--- /dev/null
+++ b/tests/unit/test_gerrit_legacy_crd.py
@@ -0,0 +1,629 @@
+#!/usr/bin/env python
+
+# Copyright 2012 Hewlett-Packard Development Company, L.P.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+from tests.base import (
+    ZuulTestCase,
+    simple_layout,
+)
+
+
+class TestGerritLegacyCRD(ZuulTestCase):
+    tenant_config_file = 'config/single-tenant/main.yaml'
+
+    def test_crd_gate(self):
+        "Test cross-repo dependencies"
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
+        A.addApproval('Code-Review', 2)
+        B.addApproval('Code-Review', 2)
+
+        AM2 = self.fake_gerrit.addFakeChange('org/project1', 'master', 'AM2')
+        AM1 = self.fake_gerrit.addFakeChange('org/project1', 'master', 'AM1')
+        AM2.setMerged()
+        AM1.setMerged()
+
+        BM2 = self.fake_gerrit.addFakeChange('org/project2', 'master', 'BM2')
+        BM1 = self.fake_gerrit.addFakeChange('org/project2', 'master', 'BM1')
+        BM2.setMerged()
+        BM1.setMerged()
+
+        # A -> AM1 -> AM2
+        # B -> BM1 -> BM2
+        # A Depends-On: B
+        # M2 is here to make sure it is never queried.  If it is, it
+        # means zuul is walking down the entire history of merged
+        # changes.
+
+        B.setDependsOn(BM1, 1)
+        BM1.setDependsOn(BM2, 1)
+
+        A.setDependsOn(AM1, 1)
+        AM1.setDependsOn(AM2, 1)
+
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['id'])
+
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+
+        for connection in self.connections.connections.values():
+            connection.maintainCache([])
+
+        self.executor_server.hold_jobs_in_build = True
+        B.addApproval('Approved', 1)
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(AM2.queried, 0)
+        self.assertEqual(BM2.queried, 0)
+        self.assertEqual(A.data['status'], 'MERGED')
+        self.assertEqual(B.data['status'], 'MERGED')
+        self.assertEqual(A.reported, 2)
+        self.assertEqual(B.reported, 2)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'org/project1').changes
+        self.assertEqual(changes, '2,1 1,1')
+
+    def test_crd_branch(self):
+        "Test cross-repo dependencies in multiple branches"
+
+        self.create_branch('org/project2', 'mp')
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
+        C1 = self.fake_gerrit.addFakeChange('org/project2', 'mp', 'C1')
+        C2 = self.fake_gerrit.addFakeChange('org/project2', 'mp', 'C2',
+                                            status='ABANDONED')
+        C1.data['id'] = B.data['id']
+        C2.data['id'] = B.data['id']
+
+        A.addApproval('Code-Review', 2)
+        B.addApproval('Code-Review', 2)
+        C1.addApproval('Code-Review', 2)
+
+        # A Depends-On: B+C1
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['id'])
+
+        self.executor_server.hold_jobs_in_build = True
+        B.addApproval('Approved', 1)
+        C1.addApproval('Approved', 1)
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'MERGED')
+        self.assertEqual(B.data['status'], 'MERGED')
+        self.assertEqual(C1.data['status'], 'MERGED')
+        self.assertEqual(A.reported, 2)
+        self.assertEqual(B.reported, 2)
+        self.assertEqual(C1.reported, 2)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'org/project1').changes
+        self.assertEqual(changes, '2,1 3,1 1,1')
+
+    def test_crd_multiline(self):
+        "Test multiple depends-on lines in commit"
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
+        C = self.fake_gerrit.addFakeChange('org/project2', 'master', 'C')
+        A.addApproval('Code-Review', 2)
+        B.addApproval('Code-Review', 2)
+        C.addApproval('Code-Review', 2)
+
+        # A Depends-On: B+C
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\nDepends-On: %s\n' % (
+            A.subject, B.data['id'], C.data['id'])
+
+        self.executor_server.hold_jobs_in_build = True
+        B.addApproval('Approved', 1)
+        C.addApproval('Approved', 1)
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'MERGED')
+        self.assertEqual(B.data['status'], 'MERGED')
+        self.assertEqual(C.data['status'], 'MERGED')
+        self.assertEqual(A.reported, 2)
+        self.assertEqual(B.reported, 2)
+        self.assertEqual(C.reported, 2)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'org/project1').changes
+        self.assertEqual(changes, '2,1 3,1 1,1')
+
+    def test_crd_unshared_gate(self):
+        "Test cross-repo dependencies in unshared gate queues"
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project', 'master', 'B')
+        A.addApproval('Code-Review', 2)
+        B.addApproval('Code-Review', 2)
+
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['id'])
+
+        # A and B do not share a queue, make sure that A is unable to
+        # enqueue B (and therefore, A is unable to be enqueued).
+        B.addApproval('Approved', 1)
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(A.reported, 0)
+        self.assertEqual(B.reported, 0)
+        self.assertEqual(len(self.history), 0)
+
+        # Enqueue and merge B alone.
+        self.fake_gerrit.addEvent(B.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(B.data['status'], 'MERGED')
+        self.assertEqual(B.reported, 2)
+
+        # Now that B is merged, A should be able to be enqueued and
+        # merged.
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'MERGED')
+        self.assertEqual(A.reported, 2)
+
+    def test_crd_gate_reverse(self):
+        "Test reverse cross-repo dependencies"
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
+        A.addApproval('Code-Review', 2)
+        B.addApproval('Code-Review', 2)
+
+        # A Depends-On: B
+
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['id'])
+
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+
+        self.executor_server.hold_jobs_in_build = True
+        A.addApproval('Approved', 1)
+        self.fake_gerrit.addEvent(B.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'MERGED')
+        self.assertEqual(B.data['status'], 'MERGED')
+        self.assertEqual(A.reported, 2)
+        self.assertEqual(B.reported, 2)
+
+        changes = self.getJobFromHistory(
+            'project-merge', 'org/project1').changes
+        self.assertEqual(changes, '2,1 1,1')
+
+    def test_crd_cycle(self):
+        "Test cross-repo dependency cycles"
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
+        A.addApproval('Code-Review', 2)
+        B.addApproval('Code-Review', 2)
+
+        # A -> B -> A (via commit-depends)
+
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['id'])
+        B.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            B.subject, A.data['id'])
+
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.reported, 0)
+        self.assertEqual(B.reported, 0)
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+
+    def test_crd_gate_unknown(self):
+        "Test unknown projects in dependent pipeline"
+        self.init_repo("org/unknown", tag='init')
+        A = self.fake_gerrit.addFakeChange('org/project', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/unknown', 'master', 'B')
+        A.addApproval('Code-Review', 2)
+        B.addApproval('Code-Review', 2)
+
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['id'])
+
+        B.addApproval('Approved', 1)
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        # Unknown projects cannot share a queue with any other
+        # since they don't have common jobs with any other (they have no jobs).
+        # Changes which depend on unknown project changes
+        # should not be processed in dependent pipeline
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(A.reported, 0)
+        self.assertEqual(B.reported, 0)
+        self.assertEqual(len(self.history), 0)
+
+        # Simulate change B being gated outside this layout Set the
+        # change merged before submitting the event so that when the
+        # event triggers a gerrit query to update the change, we get
+        # the information that it was merged.
+        B.setMerged()
+        self.fake_gerrit.addEvent(B.addApproval('Approved', 1))
+        self.waitUntilSettled()
+        self.assertEqual(len(self.history), 0)
+
+        # Now that B is merged, A should be able to be enqueued and
+        # merged.
+        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'MERGED')
+        self.assertEqual(A.reported, 2)
+        self.assertEqual(B.data['status'], 'MERGED')
+        self.assertEqual(B.reported, 0)
+
+    def test_crd_check(self):
+        "Test cross-repo dependencies in independent pipelines"
+
+        self.executor_server.hold_jobs_in_build = True
+        self.gearman_server.hold_jobs_in_queue = True
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
+
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['id'])
+
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        self.gearman_server.hold_jobs_in_queue = False
+        self.gearman_server.release()
+        self.waitUntilSettled()
+
+        self.executor_server.release('.*-merge')
+        self.waitUntilSettled()
+
+        self.assertTrue(self.builds[0].hasChanges(A, B))
+
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(A.reported, 1)
+        self.assertEqual(B.reported, 0)
+
+        self.assertEqual(self.history[0].changes, '2,1 1,1')
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 0)
+
+    def test_crd_check_git_depends(self):
+        "Test single-repo dependencies in independent pipelines"
+        self.gearman_server.hold_jobs_in_build = True
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project1', 'master', 'B')
+
+        # Add two git-dependent changes and make sure they both report
+        # success.
+        B.setDependsOn(A, 1)
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        self.orderedRelease()
+        self.gearman_server.hold_jobs_in_build = False
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(A.reported, 1)
+        self.assertEqual(B.reported, 1)
+
+        self.assertEqual(self.history[0].changes, '1,1')
+        self.assertEqual(self.history[-1].changes, '1,1 2,1')
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 0)
+
+        self.assertIn('Build succeeded', A.messages[0])
+        self.assertIn('Build succeeded', B.messages[0])
+
+    def test_crd_check_duplicate(self):
+        "Test duplicate check in independent pipelines"
+        self.executor_server.hold_jobs_in_build = True
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project1', 'master', 'B')
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        check_pipeline = tenant.layout.pipelines['check']
+
+        # Add two git-dependent changes...
+        B.setDependsOn(A, 1)
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(len(check_pipeline.getAllItems()), 2)
+
+        # ...make sure the live one is not duplicated...
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(len(check_pipeline.getAllItems()), 2)
+
+        # ...but the non-live one is able to be.
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(len(check_pipeline.getAllItems()), 3)
+
+        # Release jobs in order to avoid races with change A jobs
+        # finishing before change B jobs.
+        self.orderedRelease()
+        self.executor_server.hold_jobs_in_build = False
+        self.executor_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(A.reported, 1)
+        self.assertEqual(B.reported, 1)
+
+        self.assertEqual(self.history[0].changes, '1,1 2,1')
+        self.assertEqual(self.history[1].changes, '1,1')
+        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 0)
+
+        self.assertIn('Build succeeded', A.messages[0])
+        self.assertIn('Build succeeded', B.messages[0])
+
+    def _test_crd_check_reconfiguration(self, project1, project2):
+        "Test cross-repo dependencies re-enqueued in independent pipelines"
+
+        self.gearman_server.hold_jobs_in_queue = True
+        A = self.fake_gerrit.addFakeChange(project1, 'master', 'A')
+        B = self.fake_gerrit.addFakeChange(project2, 'master', 'B')
+
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['id'])
+
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        self.sched.reconfigure(self.config)
+
+        # Make sure the items still share a change queue, and the
+        # first one is not live.
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 1)
+        queue = tenant.layout.pipelines['check'].queues[0]
+        first_item = queue.queue[0]
+        for item in queue.queue:
+            self.assertEqual(item.queue, first_item.queue)
+        self.assertFalse(first_item.live)
+        self.assertTrue(queue.queue[1].live)
+
+        self.gearman_server.hold_jobs_in_queue = False
+        self.gearman_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(A.reported, 1)
+        self.assertEqual(B.reported, 0)
+
+        self.assertEqual(self.history[0].changes, '2,1 1,1')
+        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 0)
+
+    def test_crd_check_reconfiguration(self):
+        self._test_crd_check_reconfiguration('org/project1', 'org/project2')
+
+    def test_crd_undefined_project(self):
+        """Test that undefined projects in dependencies are handled for
+        independent pipelines"""
+        # It's a hack for fake gerrit,
+        # as it implies repo creation upon the creation of any change
+        self.init_repo("org/unknown", tag='init')
+        self._test_crd_check_reconfiguration('org/project1', 'org/unknown')
+
+    @simple_layout('layouts/ignore-dependencies.yaml')
+    def test_crd_check_ignore_dependencies(self):
+        "Test cross-repo dependencies can be ignored"
+
+        self.gearman_server.hold_jobs_in_queue = True
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
+        C = self.fake_gerrit.addFakeChange('org/project2', 'master', 'C')
+
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['id'])
+        # C git-depends on B
+        C.setDependsOn(B, 1)
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+        self.fake_gerrit.addEvent(C.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        # Make sure none of the items share a change queue, and all
+        # are live.
+        tenant = self.sched.abide.tenants.get('tenant-one')
+        check_pipeline = tenant.layout.pipelines['check']
+        self.assertEqual(len(check_pipeline.queues), 3)
+        self.assertEqual(len(check_pipeline.getAllItems()), 3)
+        for item in check_pipeline.getAllItems():
+            self.assertTrue(item.live)
+
+        self.gearman_server.hold_jobs_in_queue = False
+        self.gearman_server.release()
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(C.data['status'], 'NEW')
+        self.assertEqual(A.reported, 1)
+        self.assertEqual(B.reported, 1)
+        self.assertEqual(C.reported, 1)
+
+        # Each job should have tested exactly one change
+        for job in self.history:
+            self.assertEqual(len(job.changes.split()), 1)
+
+    @simple_layout('layouts/three-projects.yaml')
+    def test_crd_check_transitive(self):
+        "Test transitive cross-repo dependencies"
+        # Specifically, if A -> B -> C, and C gets a new patchset and
+        # A gets a new patchset, ensure the test of A,2 includes B,1
+        # and C,2 (not C,1 which would indicate stale data in the
+        # cache for B).
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
+        C = self.fake_gerrit.addFakeChange('org/project3', 'master', 'C')
+
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['id'])
+
+        # B Depends-On: C
+        B.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            B.subject, C.data['id'])
+
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '3,1 2,1 1,1')
+
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '3,1 2,1')
+
+        self.fake_gerrit.addEvent(C.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '3,1')
+
+        C.addPatchset()
+        self.fake_gerrit.addEvent(C.getPatchsetCreatedEvent(2))
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '3,2')
+
+        A.addPatchset()
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(2))
+        self.waitUntilSettled()
+        self.assertEqual(self.history[-1].changes, '3,2 2,1 1,2')
+
+    def test_crd_check_unknown(self):
+        "Test unknown projects in independent pipeline"
+        self.init_repo("org/unknown", tag='init')
+        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
+        B = self.fake_gerrit.addFakeChange('org/unknown', 'master', 'D')
+        # A Depends-On: B
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['id'])
+
+        # Make sure zuul has seen an event on B.
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        self.assertEqual(A.data['status'], 'NEW')
+        self.assertEqual(A.reported, 1)
+        self.assertEqual(B.data['status'], 'NEW')
+        self.assertEqual(B.reported, 0)
+
+    def test_crd_cycle_join(self):
+        "Test an updated change creates a cycle"
+        A = self.fake_gerrit.addFakeChange('org/project2', 'master', 'A')
+
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+        self.assertEqual(A.reported, 1)
+
+        # Create B->A
+        B = self.fake_gerrit.addFakeChange('org/project1', 'master', 'B')
+        B.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            B.subject, A.data['id'])
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        # Dep is there so zuul should have reported on B
+        self.assertEqual(B.reported, 1)
+
+        # Update A to add A->B (a cycle).
+        A.addPatchset()
+        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
+            A.subject, B.data['id'])
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(2))
+        self.waitUntilSettled()
+
+        # Dependency cycle injected so zuul should not have reported again on A
+        self.assertEqual(A.reported, 1)
+
+        # Now if we update B to remove the depends-on, everything
+        # should be okay.  B; A->B
+
+        B.addPatchset()
+        B.data['commitMessage'] = '%s\n' % (B.subject,)
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(2))
+        self.waitUntilSettled()
+
+        # Cycle was removed so now zuul should have reported again on A
+        self.assertEqual(A.reported, 2)
+
+        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(2))
+        self.waitUntilSettled()
+        self.assertEqual(B.reported, 2)
diff --git a/tests/unit/test_inventory.py b/tests/unit/test_inventory.py
index be50447..b7e35eb 100644
--- a/tests/unit/test_inventory.py
+++ b/tests/unit/test_inventory.py
@@ -37,6 +37,12 @@
         inv_path = os.path.join(build.jobdir.root, 'ansible', 'inventory.yaml')
         return yaml.safe_load(open(inv_path, 'r'))
 
+    def _get_setup_inventory(self, name):
+        build = self.getBuildByName(name)
+        setup_inv_path = os.path.join(build.jobdir.root, 'ansible',
+                                      'setup-inventory.yaml')
+        return yaml.safe_load(open(setup_inv_path, 'r'))
+
     def test_single_inventory(self):
 
         inventory = self._get_build_inventory('single-inventory')
@@ -131,3 +137,23 @@
 
         self.executor_server.release()
         self.waitUntilSettled()
+
+    def test_setup_inventory(self):
+
+        setup_inventory = self._get_setup_inventory('hostvars-inventory')
+        inventory = self._get_build_inventory('hostvars-inventory')
+
+        self.assertIn('all', inventory)
+        self.assertIn('hosts', inventory['all'])
+
+        self.assertIn('default', setup_inventory['all']['hosts'])
+        self.assertIn('fakeuser', setup_inventory['all']['hosts'])
+        self.assertIn('windows', setup_inventory['all']['hosts'])
+        self.assertNotIn('network', setup_inventory['all']['hosts'])
+        self.assertIn('default', inventory['all']['hosts'])
+        self.assertIn('fakeuser', inventory['all']['hosts'])
+        self.assertIn('windows', inventory['all']['hosts'])
+        self.assertIn('network', inventory['all']['hosts'])
+
+        self.executor_server.release()
+        self.waitUntilSettled()
diff --git a/tests/unit/test_scheduler.py b/tests/unit/test_scheduler.py
index 6bbf098..5db20b3 100755
--- a/tests/unit/test_scheduler.py
+++ b/tests/unit/test_scheduler.py
@@ -4196,7 +4196,7 @@
         running_item = running_items[0]
         self.assertEqual([], running_item['failing_reasons'])
         self.assertEqual([], running_item['items_behind'])
-        self.assertEqual('https://hostname/1', running_item['url'])
+        self.assertEqual('https://review.example.com/1', running_item['url'])
         self.assertIsNone(running_item['item_ahead'])
         self.assertEqual('org/project', running_item['project'])
         self.assertIsNone(running_item['remaining_time'])
@@ -4247,611 +4247,6 @@
             'SUCCESS')
         self.assertEqual(A.reported, 1)
 
-    def test_crd_gate(self):
-        "Test cross-repo dependencies"
-        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
-        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
-        A.addApproval('Code-Review', 2)
-        B.addApproval('Code-Review', 2)
-
-        AM2 = self.fake_gerrit.addFakeChange('org/project1', 'master', 'AM2')
-        AM1 = self.fake_gerrit.addFakeChange('org/project1', 'master', 'AM1')
-        AM2.setMerged()
-        AM1.setMerged()
-
-        BM2 = self.fake_gerrit.addFakeChange('org/project2', 'master', 'BM2')
-        BM1 = self.fake_gerrit.addFakeChange('org/project2', 'master', 'BM1')
-        BM2.setMerged()
-        BM1.setMerged()
-
-        # A -> AM1 -> AM2
-        # B -> BM1 -> BM2
-        # A Depends-On: B
-        # M2 is here to make sure it is never queried.  If it is, it
-        # means zuul is walking down the entire history of merged
-        # changes.
-
-        B.setDependsOn(BM1, 1)
-        BM1.setDependsOn(BM2, 1)
-
-        A.setDependsOn(AM1, 1)
-        AM1.setDependsOn(AM2, 1)
-
-        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
-            A.subject, B.data['id'])
-
-        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
-        self.waitUntilSettled()
-
-        self.assertEqual(A.data['status'], 'NEW')
-        self.assertEqual(B.data['status'], 'NEW')
-
-        for connection in self.connections.connections.values():
-            connection.maintainCache([])
-
-        self.executor_server.hold_jobs_in_build = True
-        B.addApproval('Approved', 1)
-        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
-        self.waitUntilSettled()
-
-        self.executor_server.release('.*-merge')
-        self.waitUntilSettled()
-        self.executor_server.release('.*-merge')
-        self.waitUntilSettled()
-        self.executor_server.hold_jobs_in_build = False
-        self.executor_server.release()
-        self.waitUntilSettled()
-
-        self.assertEqual(AM2.queried, 0)
-        self.assertEqual(BM2.queried, 0)
-        self.assertEqual(A.data['status'], 'MERGED')
-        self.assertEqual(B.data['status'], 'MERGED')
-        self.assertEqual(A.reported, 2)
-        self.assertEqual(B.reported, 2)
-
-        changes = self.getJobFromHistory(
-            'project-merge', 'org/project1').changes
-        self.assertEqual(changes, '2,1 1,1')
-
-    def test_crd_branch(self):
-        "Test cross-repo dependencies in multiple branches"
-
-        self.create_branch('org/project2', 'mp')
-        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
-        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
-        C1 = self.fake_gerrit.addFakeChange('org/project2', 'mp', 'C1')
-        C2 = self.fake_gerrit.addFakeChange('org/project2', 'mp', 'C2',
-                                            status='ABANDONED')
-        C1.data['id'] = B.data['id']
-        C2.data['id'] = B.data['id']
-
-        A.addApproval('Code-Review', 2)
-        B.addApproval('Code-Review', 2)
-        C1.addApproval('Code-Review', 2)
-
-        # A Depends-On: B+C1
-        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
-            A.subject, B.data['id'])
-
-        self.executor_server.hold_jobs_in_build = True
-        B.addApproval('Approved', 1)
-        C1.addApproval('Approved', 1)
-        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
-        self.waitUntilSettled()
-
-        self.executor_server.release('.*-merge')
-        self.waitUntilSettled()
-        self.executor_server.release('.*-merge')
-        self.waitUntilSettled()
-        self.executor_server.release('.*-merge')
-        self.waitUntilSettled()
-        self.executor_server.hold_jobs_in_build = False
-        self.executor_server.release()
-        self.waitUntilSettled()
-
-        self.assertEqual(A.data['status'], 'MERGED')
-        self.assertEqual(B.data['status'], 'MERGED')
-        self.assertEqual(C1.data['status'], 'MERGED')
-        self.assertEqual(A.reported, 2)
-        self.assertEqual(B.reported, 2)
-        self.assertEqual(C1.reported, 2)
-
-        changes = self.getJobFromHistory(
-            'project-merge', 'org/project1').changes
-        self.assertEqual(changes, '2,1 3,1 1,1')
-
-    def test_crd_multiline(self):
-        "Test multiple depends-on lines in commit"
-        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
-        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
-        C = self.fake_gerrit.addFakeChange('org/project2', 'master', 'C')
-        A.addApproval('Code-Review', 2)
-        B.addApproval('Code-Review', 2)
-        C.addApproval('Code-Review', 2)
-
-        # A Depends-On: B+C
-        A.data['commitMessage'] = '%s\n\nDepends-On: %s\nDepends-On: %s\n' % (
-            A.subject, B.data['id'], C.data['id'])
-
-        self.executor_server.hold_jobs_in_build = True
-        B.addApproval('Approved', 1)
-        C.addApproval('Approved', 1)
-        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
-        self.waitUntilSettled()
-
-        self.executor_server.release('.*-merge')
-        self.waitUntilSettled()
-        self.executor_server.release('.*-merge')
-        self.waitUntilSettled()
-        self.executor_server.release('.*-merge')
-        self.waitUntilSettled()
-        self.executor_server.hold_jobs_in_build = False
-        self.executor_server.release()
-        self.waitUntilSettled()
-
-        self.assertEqual(A.data['status'], 'MERGED')
-        self.assertEqual(B.data['status'], 'MERGED')
-        self.assertEqual(C.data['status'], 'MERGED')
-        self.assertEqual(A.reported, 2)
-        self.assertEqual(B.reported, 2)
-        self.assertEqual(C.reported, 2)
-
-        changes = self.getJobFromHistory(
-            'project-merge', 'org/project1').changes
-        self.assertEqual(changes, '2,1 3,1 1,1')
-
-    def test_crd_unshared_gate(self):
-        "Test cross-repo dependencies in unshared gate queues"
-        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
-        B = self.fake_gerrit.addFakeChange('org/project', 'master', 'B')
-        A.addApproval('Code-Review', 2)
-        B.addApproval('Code-Review', 2)
-
-        # A Depends-On: B
-        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
-            A.subject, B.data['id'])
-
-        # A and B do not share a queue, make sure that A is unable to
-        # enqueue B (and therefore, A is unable to be enqueued).
-        B.addApproval('Approved', 1)
-        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
-        self.waitUntilSettled()
-
-        self.assertEqual(A.data['status'], 'NEW')
-        self.assertEqual(B.data['status'], 'NEW')
-        self.assertEqual(A.reported, 0)
-        self.assertEqual(B.reported, 0)
-        self.assertEqual(len(self.history), 0)
-
-        # Enqueue and merge B alone.
-        self.fake_gerrit.addEvent(B.addApproval('Approved', 1))
-        self.waitUntilSettled()
-
-        self.assertEqual(B.data['status'], 'MERGED')
-        self.assertEqual(B.reported, 2)
-
-        # Now that B is merged, A should be able to be enqueued and
-        # merged.
-        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
-        self.waitUntilSettled()
-
-        self.assertEqual(A.data['status'], 'MERGED')
-        self.assertEqual(A.reported, 2)
-
-    def test_crd_gate_reverse(self):
-        "Test reverse cross-repo dependencies"
-        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
-        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
-        A.addApproval('Code-Review', 2)
-        B.addApproval('Code-Review', 2)
-
-        # A Depends-On: B
-
-        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
-            A.subject, B.data['id'])
-
-        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
-        self.waitUntilSettled()
-
-        self.assertEqual(A.data['status'], 'NEW')
-        self.assertEqual(B.data['status'], 'NEW')
-
-        self.executor_server.hold_jobs_in_build = True
-        A.addApproval('Approved', 1)
-        self.fake_gerrit.addEvent(B.addApproval('Approved', 1))
-        self.waitUntilSettled()
-
-        self.executor_server.release('.*-merge')
-        self.waitUntilSettled()
-        self.executor_server.release('.*-merge')
-        self.waitUntilSettled()
-        self.executor_server.hold_jobs_in_build = False
-        self.executor_server.release()
-        self.waitUntilSettled()
-
-        self.assertEqual(A.data['status'], 'MERGED')
-        self.assertEqual(B.data['status'], 'MERGED')
-        self.assertEqual(A.reported, 2)
-        self.assertEqual(B.reported, 2)
-
-        changes = self.getJobFromHistory(
-            'project-merge', 'org/project1').changes
-        self.assertEqual(changes, '2,1 1,1')
-
-    def test_crd_cycle(self):
-        "Test cross-repo dependency cycles"
-        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
-        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
-        A.addApproval('Code-Review', 2)
-        B.addApproval('Code-Review', 2)
-
-        # A -> B -> A (via commit-depends)
-
-        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
-            A.subject, B.data['id'])
-        B.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
-            B.subject, A.data['id'])
-
-        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
-        self.waitUntilSettled()
-
-        self.assertEqual(A.reported, 0)
-        self.assertEqual(B.reported, 0)
-        self.assertEqual(A.data['status'], 'NEW')
-        self.assertEqual(B.data['status'], 'NEW')
-
-    def test_crd_gate_unknown(self):
-        "Test unknown projects in dependent pipeline"
-        self.init_repo("org/unknown", tag='init')
-        A = self.fake_gerrit.addFakeChange('org/project', 'master', 'A')
-        B = self.fake_gerrit.addFakeChange('org/unknown', 'master', 'B')
-        A.addApproval('Code-Review', 2)
-        B.addApproval('Code-Review', 2)
-
-        # A Depends-On: B
-        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
-            A.subject, B.data['id'])
-
-        B.addApproval('Approved', 1)
-        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
-        self.waitUntilSettled()
-
-        # Unknown projects cannot share a queue with any other
-        # since they don't have common jobs with any other (they have no jobs).
-        # Changes which depend on unknown project changes
-        # should not be processed in dependent pipeline
-        self.assertEqual(A.data['status'], 'NEW')
-        self.assertEqual(B.data['status'], 'NEW')
-        self.assertEqual(A.reported, 0)
-        self.assertEqual(B.reported, 0)
-        self.assertEqual(len(self.history), 0)
-
-        # Simulate change B being gated outside this layout Set the
-        # change merged before submitting the event so that when the
-        # event triggers a gerrit query to update the change, we get
-        # the information that it was merged.
-        B.setMerged()
-        self.fake_gerrit.addEvent(B.addApproval('Approved', 1))
-        self.waitUntilSettled()
-        self.assertEqual(len(self.history), 0)
-
-        # Now that B is merged, A should be able to be enqueued and
-        # merged.
-        self.fake_gerrit.addEvent(A.addApproval('Approved', 1))
-        self.waitUntilSettled()
-
-        self.assertEqual(A.data['status'], 'MERGED')
-        self.assertEqual(A.reported, 2)
-        self.assertEqual(B.data['status'], 'MERGED')
-        self.assertEqual(B.reported, 0)
-
-    def test_crd_check(self):
-        "Test cross-repo dependencies in independent pipelines"
-
-        self.executor_server.hold_jobs_in_build = True
-        self.gearman_server.hold_jobs_in_queue = True
-        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
-        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
-
-        # A Depends-On: B
-        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
-            A.subject, B.data['id'])
-
-        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
-        self.waitUntilSettled()
-
-        self.gearman_server.hold_jobs_in_queue = False
-        self.gearman_server.release()
-        self.waitUntilSettled()
-
-        self.executor_server.release('.*-merge')
-        self.waitUntilSettled()
-
-        self.assertTrue(self.builds[0].hasChanges(A, B))
-
-        self.executor_server.hold_jobs_in_build = False
-        self.executor_server.release()
-        self.waitUntilSettled()
-
-        self.assertEqual(A.data['status'], 'NEW')
-        self.assertEqual(B.data['status'], 'NEW')
-        self.assertEqual(A.reported, 1)
-        self.assertEqual(B.reported, 0)
-
-        self.assertEqual(self.history[0].changes, '2,1 1,1')
-        tenant = self.sched.abide.tenants.get('tenant-one')
-        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 0)
-
-    def test_crd_check_git_depends(self):
-        "Test single-repo dependencies in independent pipelines"
-        self.gearman_server.hold_jobs_in_build = True
-        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
-        B = self.fake_gerrit.addFakeChange('org/project1', 'master', 'B')
-
-        # Add two git-dependent changes and make sure they both report
-        # success.
-        B.setDependsOn(A, 1)
-        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
-        self.waitUntilSettled()
-        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
-        self.waitUntilSettled()
-
-        self.orderedRelease()
-        self.gearman_server.hold_jobs_in_build = False
-        self.waitUntilSettled()
-
-        self.assertEqual(A.data['status'], 'NEW')
-        self.assertEqual(B.data['status'], 'NEW')
-        self.assertEqual(A.reported, 1)
-        self.assertEqual(B.reported, 1)
-
-        self.assertEqual(self.history[0].changes, '1,1')
-        self.assertEqual(self.history[-1].changes, '1,1 2,1')
-        tenant = self.sched.abide.tenants.get('tenant-one')
-        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 0)
-
-        self.assertIn('Build succeeded', A.messages[0])
-        self.assertIn('Build succeeded', B.messages[0])
-
-    def test_crd_check_duplicate(self):
-        "Test duplicate check in independent pipelines"
-        self.executor_server.hold_jobs_in_build = True
-        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
-        B = self.fake_gerrit.addFakeChange('org/project1', 'master', 'B')
-        tenant = self.sched.abide.tenants.get('tenant-one')
-        check_pipeline = tenant.layout.pipelines['check']
-
-        # Add two git-dependent changes...
-        B.setDependsOn(A, 1)
-        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
-        self.waitUntilSettled()
-        self.assertEqual(len(check_pipeline.getAllItems()), 2)
-
-        # ...make sure the live one is not duplicated...
-        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
-        self.waitUntilSettled()
-        self.assertEqual(len(check_pipeline.getAllItems()), 2)
-
-        # ...but the non-live one is able to be.
-        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
-        self.waitUntilSettled()
-        self.assertEqual(len(check_pipeline.getAllItems()), 3)
-
-        # Release jobs in order to avoid races with change A jobs
-        # finishing before change B jobs.
-        self.orderedRelease()
-        self.executor_server.hold_jobs_in_build = False
-        self.executor_server.release()
-        self.waitUntilSettled()
-
-        self.assertEqual(A.data['status'], 'NEW')
-        self.assertEqual(B.data['status'], 'NEW')
-        self.assertEqual(A.reported, 1)
-        self.assertEqual(B.reported, 1)
-
-        self.assertEqual(self.history[0].changes, '1,1 2,1')
-        self.assertEqual(self.history[1].changes, '1,1')
-        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 0)
-
-        self.assertIn('Build succeeded', A.messages[0])
-        self.assertIn('Build succeeded', B.messages[0])
-
-    def _test_crd_check_reconfiguration(self, project1, project2):
-        "Test cross-repo dependencies re-enqueued in independent pipelines"
-
-        self.gearman_server.hold_jobs_in_queue = True
-        A = self.fake_gerrit.addFakeChange(project1, 'master', 'A')
-        B = self.fake_gerrit.addFakeChange(project2, 'master', 'B')
-
-        # A Depends-On: B
-        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
-            A.subject, B.data['id'])
-
-        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
-        self.waitUntilSettled()
-
-        self.sched.reconfigure(self.config)
-
-        # Make sure the items still share a change queue, and the
-        # first one is not live.
-        tenant = self.sched.abide.tenants.get('tenant-one')
-        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 1)
-        queue = tenant.layout.pipelines['check'].queues[0]
-        first_item = queue.queue[0]
-        for item in queue.queue:
-            self.assertEqual(item.queue, first_item.queue)
-        self.assertFalse(first_item.live)
-        self.assertTrue(queue.queue[1].live)
-
-        self.gearman_server.hold_jobs_in_queue = False
-        self.gearman_server.release()
-        self.waitUntilSettled()
-
-        self.assertEqual(A.data['status'], 'NEW')
-        self.assertEqual(B.data['status'], 'NEW')
-        self.assertEqual(A.reported, 1)
-        self.assertEqual(B.reported, 0)
-
-        self.assertEqual(self.history[0].changes, '2,1 1,1')
-        self.assertEqual(len(tenant.layout.pipelines['check'].queues), 0)
-
-    def test_crd_check_reconfiguration(self):
-        self._test_crd_check_reconfiguration('org/project1', 'org/project2')
-
-    def test_crd_undefined_project(self):
-        """Test that undefined projects in dependencies are handled for
-        independent pipelines"""
-        # It's a hack for fake gerrit,
-        # as it implies repo creation upon the creation of any change
-        self.init_repo("org/unknown", tag='init')
-        self._test_crd_check_reconfiguration('org/project1', 'org/unknown')
-
-    @simple_layout('layouts/ignore-dependencies.yaml')
-    def test_crd_check_ignore_dependencies(self):
-        "Test cross-repo dependencies can be ignored"
-
-        self.gearman_server.hold_jobs_in_queue = True
-        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
-        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
-        C = self.fake_gerrit.addFakeChange('org/project2', 'master', 'C')
-
-        # A Depends-On: B
-        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
-            A.subject, B.data['id'])
-        # C git-depends on B
-        C.setDependsOn(B, 1)
-        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
-        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
-        self.fake_gerrit.addEvent(C.getPatchsetCreatedEvent(1))
-        self.waitUntilSettled()
-
-        # Make sure none of the items share a change queue, and all
-        # are live.
-        tenant = self.sched.abide.tenants.get('tenant-one')
-        check_pipeline = tenant.layout.pipelines['check']
-        self.assertEqual(len(check_pipeline.queues), 3)
-        self.assertEqual(len(check_pipeline.getAllItems()), 3)
-        for item in check_pipeline.getAllItems():
-            self.assertTrue(item.live)
-
-        self.gearman_server.hold_jobs_in_queue = False
-        self.gearman_server.release()
-        self.waitUntilSettled()
-
-        self.assertEqual(A.data['status'], 'NEW')
-        self.assertEqual(B.data['status'], 'NEW')
-        self.assertEqual(C.data['status'], 'NEW')
-        self.assertEqual(A.reported, 1)
-        self.assertEqual(B.reported, 1)
-        self.assertEqual(C.reported, 1)
-
-        # Each job should have tested exactly one change
-        for job in self.history:
-            self.assertEqual(len(job.changes.split()), 1)
-
-    @simple_layout('layouts/three-projects.yaml')
-    def test_crd_check_transitive(self):
-        "Test transitive cross-repo dependencies"
-        # Specifically, if A -> B -> C, and C gets a new patchset and
-        # A gets a new patchset, ensure the test of A,2 includes B,1
-        # and C,2 (not C,1 which would indicate stale data in the
-        # cache for B).
-        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
-        B = self.fake_gerrit.addFakeChange('org/project2', 'master', 'B')
-        C = self.fake_gerrit.addFakeChange('org/project3', 'master', 'C')
-
-        # A Depends-On: B
-        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
-            A.subject, B.data['id'])
-
-        # B Depends-On: C
-        B.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
-            B.subject, C.data['id'])
-
-        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
-        self.waitUntilSettled()
-        self.assertEqual(self.history[-1].changes, '3,1 2,1 1,1')
-
-        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
-        self.waitUntilSettled()
-        self.assertEqual(self.history[-1].changes, '3,1 2,1')
-
-        self.fake_gerrit.addEvent(C.getPatchsetCreatedEvent(1))
-        self.waitUntilSettled()
-        self.assertEqual(self.history[-1].changes, '3,1')
-
-        C.addPatchset()
-        self.fake_gerrit.addEvent(C.getPatchsetCreatedEvent(2))
-        self.waitUntilSettled()
-        self.assertEqual(self.history[-1].changes, '3,2')
-
-        A.addPatchset()
-        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(2))
-        self.waitUntilSettled()
-        self.assertEqual(self.history[-1].changes, '3,2 2,1 1,2')
-
-    def test_crd_check_unknown(self):
-        "Test unknown projects in independent pipeline"
-        self.init_repo("org/unknown", tag='init')
-        A = self.fake_gerrit.addFakeChange('org/project1', 'master', 'A')
-        B = self.fake_gerrit.addFakeChange('org/unknown', 'master', 'D')
-        # A Depends-On: B
-        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
-            A.subject, B.data['id'])
-
-        # Make sure zuul has seen an event on B.
-        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
-        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
-        self.waitUntilSettled()
-
-        self.assertEqual(A.data['status'], 'NEW')
-        self.assertEqual(A.reported, 1)
-        self.assertEqual(B.data['status'], 'NEW')
-        self.assertEqual(B.reported, 0)
-
-    def test_crd_cycle_join(self):
-        "Test an updated change creates a cycle"
-        A = self.fake_gerrit.addFakeChange('org/project2', 'master', 'A')
-
-        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
-        self.waitUntilSettled()
-        self.assertEqual(A.reported, 1)
-
-        # Create B->A
-        B = self.fake_gerrit.addFakeChange('org/project1', 'master', 'B')
-        B.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
-            B.subject, A.data['id'])
-        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(1))
-        self.waitUntilSettled()
-
-        # Dep is there so zuul should have reported on B
-        self.assertEqual(B.reported, 1)
-
-        # Update A to add A->B (a cycle).
-        A.addPatchset()
-        A.data['commitMessage'] = '%s\n\nDepends-On: %s\n' % (
-            A.subject, B.data['id'])
-        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(2))
-        self.waitUntilSettled()
-
-        # Dependency cycle injected so zuul should not have reported again on A
-        self.assertEqual(A.reported, 1)
-
-        # Now if we update B to remove the depends-on, everything
-        # should be okay.  B; A->B
-
-        B.addPatchset()
-        B.data['commitMessage'] = '%s\n' % (B.subject,)
-        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(2))
-        self.waitUntilSettled()
-
-        # Cycle was removed so now zuul should have reported again on A
-        self.assertEqual(A.reported, 2)
-
-        self.fake_gerrit.addEvent(B.getPatchsetCreatedEvent(2))
-        self.waitUntilSettled()
-        self.assertEqual(B.reported, 2)
-
     @simple_layout('layouts/disable_at.yaml')
     def test_disable_at(self):
         "Test a pipeline will only report to the disabled trigger when failing"
diff --git a/tests/unit/test_streaming.py b/tests/unit/test_streaming.py
index 59dd8b0..b999106 100644
--- a/tests/unit/test_streaming.py
+++ b/tests/unit/test_streaming.py
@@ -41,13 +41,13 @@
     def startStreamer(self, port, root=None):
         if not root:
             root = tempfile.gettempdir()
-        return zuul.lib.log_streamer.LogStreamer(None, self.host, port, root)
+        return zuul.lib.log_streamer.LogStreamer(self.host, port, root)
 
     def test_start_stop(self):
-        port = 7900
-        streamer = self.startStreamer(port)
+        streamer = self.startStreamer(0)
         self.addCleanup(streamer.stop)
 
+        port = streamer.server.socket.getsockname()[1]
         s = socket.create_connection((self.host, port))
         s.close()
 
@@ -77,8 +77,9 @@
     def startStreamer(self, port, build_uuid, root=None):
         if not root:
             root = tempfile.gettempdir()
-        self.streamer = zuul.lib.log_streamer.LogStreamer(None, self.host,
+        self.streamer = zuul.lib.log_streamer.LogStreamer(self.host,
                                                           port, root)
+        port = self.streamer.server.socket.getsockname()[1]
         s = socket.create_connection((self.host, port))
         self.addCleanup(s.close)
 
@@ -129,10 +130,9 @@
 
         # Create a thread to stream the log. We need this to be happening
         # before we create the flag file to tell the job to complete.
-        port = 7901
         streamer_thread = threading.Thread(
             target=self.startStreamer,
-            args=(port, build.uuid, self.executor_server.jobdir_root,)
+            args=(0, build.uuid, self.executor_server.jobdir_root,)
         )
         streamer_thread.start()
         self.addCleanup(self.stopStreamer)
@@ -209,7 +209,7 @@
     def test_websocket_streaming(self):
         # Start the finger streamer daemon
         streamer = zuul.lib.log_streamer.LogStreamer(
-            None, self.host, 0, self.executor_server.jobdir_root)
+            self.host, 0, self.executor_server.jobdir_root)
         self.addCleanup(streamer.stop)
 
         # Need to set the streaming port before submitting the job
@@ -294,7 +294,7 @@
     def test_finger_gateway(self):
         # Start the finger streamer daemon
         streamer = zuul.lib.log_streamer.LogStreamer(
-            None, self.host, 0, self.executor_server.jobdir_root)
+            self.host, 0, self.executor_server.jobdir_root)
         self.addCleanup(streamer.stop)
         finger_port = streamer.server.socket.getsockname()[1]
 
diff --git a/tests/unit/test_zuultrigger.py b/tests/unit/test_zuultrigger.py
index 3954a21..5575853 100644
--- a/tests/unit/test_zuultrigger.py
+++ b/tests/unit/test_zuultrigger.py
@@ -126,5 +126,5 @@
             "dependencies was unable to be automatically merged with the "
             "current state of its repository. Please rebase the change and "
             "upload a new patchset.")
-        self.assertEqual(self.fake_gerrit.queries[1],
-                         "project:org/project status:open")
+        self.assertIn("project:org/project status:open",
+                      self.fake_gerrit.queries)
diff --git a/zuul/cmd/executor.py b/zuul/cmd/executor.py
index ade9715..ad7aaa8 100755
--- a/zuul/cmd/executor.py
+++ b/zuul/cmd/executor.py
@@ -14,10 +14,8 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-import grp
 import logging
 import os
-import pwd
 import sys
 import signal
 import tempfile
@@ -64,7 +62,7 @@
 
             self.log.info("Starting log streamer")
             streamer = zuul.lib.log_streamer.LogStreamer(
-                self.user, '::', self.finger_port, self.job_dir)
+                '::', self.finger_port, self.job_dir)
 
             # Keep running until the parent dies:
             pipe_read = os.fdopen(pipe_read)
@@ -76,22 +74,6 @@
             os.close(pipe_read)
             self.log_streamer_pid = child_pid
 
-    def change_privs(self):
-        '''
-        Drop our privileges to the zuul user.
-        '''
-        if os.getuid() != 0:
-            return
-        pw = pwd.getpwnam(self.user)
-        # get a list of supplementary groups for the target user, and make sure
-        # we set them when dropping privileges.
-        groups = [g.gr_gid for g in grp.getgrall() if self.user in g.gr_mem]
-        os.setgroups(groups)
-        os.setgid(pw.pw_gid)
-        os.setuid(pw.pw_uid)
-        os.chdir(pw.pw_dir)
-        os.umask(0o022)
-
     def run(self):
         if self.args.command in zuul.executor.server.COMMANDS:
             self.send_command(self.args.command)
@@ -99,8 +81,6 @@
 
         self.configure_connections(source_only=True)
 
-        self.user = get_default(self.config, 'executor', 'user', 'zuul')
-
         if self.config.has_option('executor', 'job_dir'):
             self.job_dir = os.path.expanduser(
                 self.config.get('executor', 'job_dir'))
@@ -120,7 +100,6 @@
         )
 
         self.start_log_streamer()
-        self.change_privs()
 
         ExecutorServer = zuul.executor.server.ExecutorServer
         self.executor = ExecutorServer(self.config, self.connections,
diff --git a/zuul/driver/gerrit/gerritconnection.py b/zuul/driver/gerrit/gerritconnection.py
index f4b090d..d3b3c00 100644
--- a/zuul/driver/gerrit/gerritconnection.py
+++ b/zuul/driver/gerrit/gerritconnection.py
@@ -442,8 +442,19 @@
         # In case this change is already in the history we have a
         # cyclic dependency and don't need to update ourselves again
         # as this gets done in a previous frame of the call stack.
-        # NOTE(jeblair): I don't think it's possible to hit this case
-        # anymore as all paths hit the change cache first.
+        # NOTE(jeblair): The only case where this can still be hit is
+        # when we get an event for a change with no associated
+        # patchset; for instance, when the gerrit topic is changed.
+        # In that case, we will update change 1234,None, which will be
+        # inserted into the cache as its own entry, but then we will
+        # resolve the patchset before adding it to the history list,
+        # then if there are dependencies, we can walk down and then
+        # back up to the version of this change with a patchset which
+        # will match the history list but will have bypassed the
+        # change cache because the previous object had a patchset of
+        # None.  All paths hit the change cache first.  To be able to
+        # drop history, we need to resolve the patchset on events with
+        # no patchsets before adding the entry to the change cache.
         if (history and change.number and change.patchset and
             (change.number, change.patchset) in history):
             self.log.debug("Change %s is in history" % (change,))
@@ -461,6 +472,11 @@
         change.project = self.source.getProject(data['project'])
         change.branch = data['branch']
         change.url = data['url']
+        change.uris = [
+            '%s/%s' % (self.server, change.number),
+            '%s/#/c/%s' % (self.server, change.number),
+        ]
+
         max_ps = 0
         files = []
         for ps in data['patchSets']:
@@ -481,6 +497,7 @@
         change.open = data['open']
         change.status = data['status']
         change.owner = data['owner']
+        change.message = data['commitMessage']
 
         if change.is_merged:
             # This change is merged, so we don't need to look any further
@@ -494,7 +511,8 @@
             history = history[:]
         history.append((change.number, change.patchset))
 
-        needs_changes = []
+        needs_changes = set()
+        git_needs_changes = []
         if 'dependsOn' in data:
             parts = data['dependsOn'][0]['ref'].split('/')
             dep_num, dep_ps = parts[3], parts[4]
@@ -505,8 +523,11 @@
             # already merged. So even if it is "ABANDONED", we should not
             # ignore it.
             if (not dep.is_merged) and dep not in needs_changes:
-                needs_changes.append(dep)
+                git_needs_changes.append(dep)
+                needs_changes.add(dep)
+        change.git_needs_changes = git_needs_changes
 
+        compat_needs_changes = []
         for record in self._getDependsOnFromCommit(data['commitMessage'],
                                                    change):
             dep_num = record['number']
@@ -516,10 +537,12 @@
                            (change, dep_num, dep_ps))
             dep = self._getChange(dep_num, dep_ps, history=history)
             if dep.open and dep not in needs_changes:
-                needs_changes.append(dep)
-        change.needs_changes = needs_changes
+                compat_needs_changes.append(dep)
+                needs_changes.add(dep)
+        change.compat_needs_changes = compat_needs_changes
 
-        needed_by_changes = []
+        needed_by_changes = set()
+        git_needed_by_changes = []
         if 'neededBy' in data:
             for needed in data['neededBy']:
                 parts = needed['ref'].split('/')
@@ -527,9 +550,13 @@
                 self.log.debug("Updating %s: Getting git-needed change %s,%s" %
                                (change, dep_num, dep_ps))
                 dep = self._getChange(dep_num, dep_ps, history=history)
-                if dep.open and dep.is_current_patchset:
-                    needed_by_changes.append(dep)
+                if (dep.open and dep.is_current_patchset and
+                    dep not in needed_by_changes):
+                    git_needed_by_changes.append(dep)
+                    needed_by_changes.add(dep)
+        change.git_needed_by_changes = git_needed_by_changes
 
+        compat_needed_by_changes = []
         for record in self._getNeededByFromCommit(data['id'], change):
             dep_num = record['number']
             dep_ps = record['currentPatchSet']['number']
@@ -543,9 +570,13 @@
             refresh = (dep_num, dep_ps) not in history
             dep = self._getChange(
                 dep_num, dep_ps, refresh=refresh, history=history)
-            if dep.open and dep.is_current_patchset:
-                needed_by_changes.append(dep)
-        change.needed_by_changes = needed_by_changes
+            if (dep.open and dep.is_current_patchset
+                and dep not in needed_by_changes):
+                compat_needed_by_changes.append(dep)
+                needed_by_changes.add(dep)
+        change.compat_needed_by_changes = compat_needed_by_changes
+
+        self.sched.onChangeUpdated(change)
 
         return change
 
diff --git a/zuul/driver/gerrit/gerritsource.py b/zuul/driver/gerrit/gerritsource.py
index 7141080..9e327b9 100644
--- a/zuul/driver/gerrit/gerritsource.py
+++ b/zuul/driver/gerrit/gerritsource.py
@@ -12,12 +12,15 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import re
+import urllib
 import logging
 import voluptuous as vs
 from zuul.source import BaseSource
 from zuul.model import Project
 from zuul.driver.gerrit.gerritmodel import GerritRefFilter
 from zuul.driver.util import scalar_or_list, to_list
+from zuul.lib.dependson import find_dependency_headers
 
 
 class GerritSource(BaseSource):
@@ -44,6 +47,61 @@
     def getChange(self, event, refresh=False):
         return self.connection.getChange(event, refresh)
 
+    change_re = re.compile(r"/(\#\/c\/)?(\d+)[\w]*")
+
+    def getChangeByURL(self, url):
+        try:
+            parsed = urllib.parse.urlparse(url)
+        except ValueError:
+            return None
+        m = self.change_re.match(parsed.path)
+        if not m:
+            return None
+        try:
+            change_no = int(m.group(2))
+        except ValueError:
+            return None
+        query = "change:%s" % (change_no,)
+        results = self.connection.simpleQuery(query)
+        if not results:
+            return None
+        change = self.connection._getChange(
+            results[0]['number'], results[0]['currentPatchSet']['number'])
+        return change
+
+    def getChangesDependingOn(self, change, projects):
+        changes = []
+        if not change.uris:
+            return changes
+        queries = set()
+        for uri in change.uris:
+            queries.add('message:%s' % uri)
+        query = '(' + ' OR '.join(queries) + ')'
+        results = self.connection.simpleQuery(query)
+        seen = set()
+        for result in results:
+            for match in find_dependency_headers(result['commitMessage']):
+                found = False
+                for uri in change.uris:
+                    if uri in match:
+                        found = True
+                        break
+                if not found:
+                    continue
+                key = (result['number'], result['currentPatchSet']['number'])
+                if key in seen:
+                    continue
+                seen.add(key)
+                change = self.connection._getChange(
+                    result['number'], result['currentPatchSet']['number'])
+                changes.append(change)
+        return changes
+
+    def getCachedChanges(self):
+        for x in self.connection._change_cache.values():
+            for y in x.values():
+                yield y
+
     def getProject(self, name):
         p = self.connection.getProject(name)
         if not p:
diff --git a/zuul/driver/git/gitsource.py b/zuul/driver/git/gitsource.py
index 78ae04e..a7d42be 100644
--- a/zuul/driver/git/gitsource.py
+++ b/zuul/driver/git/gitsource.py
@@ -38,6 +38,15 @@
     def getChange(self, event, refresh=False):
         return self.connection.getChange(event, refresh)
 
+    def getChangeByURL(self, url):
+        return None
+
+    def getChangesDependingOn(self, change, projects):
+        return []
+
+    def getCachedChanges(self):
+        return []
+
     def getProject(self, name):
         p = self.connection.getProject(name)
         if not p:
diff --git a/zuul/driver/github/githubconnection.py b/zuul/driver/github/githubconnection.py
index 4b91c18..a7aefe0 100644
--- a/zuul/driver/github/githubconnection.py
+++ b/zuul/driver/github/githubconnection.py
@@ -646,9 +646,12 @@
         return self._github
 
     def maintainCache(self, relevant):
+        remove = set()
         for key, change in self._change_cache.items():
             if change not in relevant:
-                del self._change_cache[key]
+                remove.add(key)
+        for key in remove:
+            del self._change_cache[key]
 
     def getChange(self, event, refresh=False):
         """Get the change representing an event."""
@@ -658,7 +661,9 @@
             change = self._getChange(project, event.change_number,
                                      event.patch_number, refresh=refresh)
             change.url = event.change_url
-            change.updated_at = self._ghTimestampToDate(event.updated_at)
+            change.uris = [
+                '%s/%s/pull/%s' % (self.server, project, change.number),
+            ]
             change.source_event = event
             change.is_current_patchset = (change.pr.get('head').get('sha') ==
                                           event.patch_number)
@@ -699,58 +704,72 @@
             raise
         return change
 
-    def _getDependsOnFromPR(self, body):
-        prs = []
-        seen = set()
+    def getChangesDependingOn(self, change, projects):
+        changes = []
+        if not change.uris:
+            return changes
 
-        for match in self.depends_on_re.findall(body):
-            if match in seen:
-                self.log.debug("Ignoring duplicate Depends-On: %s" % (match,))
-                continue
-            seen.add(match)
-            # Get the github url
-            url = match.rsplit()[-1]
-            # break it into the parts we need
-            _, org, proj, _, num = url.rsplit('/', 4)
-            # Get a pull object so we can get the head sha
-            pull = self.getPull('%s/%s' % (org, proj), int(num))
-            prs.append(pull)
+        # Get a list of projects with unique installation ids
+        installation_ids = set()
+        installation_projects = set()
 
-        return prs
+        if projects:
+            # We only need to find changes in projects in the supplied
+            # ChangeQueue.  Find all of the github installations for
+            # all of those projects, and search using each of them, so
+            # that if we get the right results based on the
+            # permissions granted to each of the installations.  The
+            # common case for this is likely to be just one
+            # installation -- change queues aren't likely to span more
+            # than one installation.
+            for project in projects:
+                installation_id = self.installation_map.get(project)
+                if installation_id not in installation_ids:
+                    installation_ids.add(installation_id)
+                    installation_projects.add(project)
+        else:
+            # We aren't in the context of a change queue and we just
+            # need to query all installations.  This currently only
+            # happens if certain features of the zuul trigger are
+            # used; generally it should be avoided.
+            for project, installation_id in self.installation_map.items():
+                if installation_id not in installation_ids:
+                    installation_ids.add(installation_id)
+                    installation_projects.add(project)
 
-    def _getNeededByFromPR(self, change):
-        prs = []
-        seen = set()
-        # This shouldn't return duplicate issues, but code as if it could
-
-        # This leaves off the protocol, but looks for the specific GitHub
-        # hostname, the org/project, and the pull request number.
-        pattern = 'Depends-On %s/%s/pull/%s' % (self.server,
-                                                change.project.name,
-                                                change.number)
+        keys = set()
+        pattern = ' OR '.join(change.uris)
         query = '%s type:pr is:open in:body' % pattern
-        # FIXME(tobiash): find a way to query this for different installations
-        github = self.getGithubClient(change.project.name)
-        for issue in github.search_issues(query=query):
-            pr = issue.issue.pull_request().as_dict()
-            if not pr.get('url'):
-                continue
-            if issue in seen:
-                continue
-            # the issue provides no good description of the project :\
-            org, proj, _, num = pr.get('url').split('/')[-4:]
-            self.log.debug("Found PR %s/%s/%s needs %s/%s" %
-                           (org, proj, num, change.project.name,
-                            change.number))
-            prs.append(pr)
-            seen.add(issue)
+        # Repeat the search for each installation id (project)
+        for installation_project in installation_projects:
+            github = self.getGithubClient(installation_project)
+            for issue in github.search_issues(query=query):
+                pr = issue.issue.pull_request().as_dict()
+                if not pr.get('url'):
+                    continue
+                # the issue provides no good description of the project :\
+                org, proj, _, num = pr.get('url').split('/')[-4:]
+                proj = pr.get('base').get('repo').get('full_name')
+                sha = pr.get('head').get('sha')
+                key = (proj, num, sha)
+                if key in keys:
+                    continue
+                self.log.debug("Found PR %s/%s needs %s/%s" %
+                               (proj, num, change.project.name,
+                                change.number))
+                keys.add(key)
+            self.log.debug("Ran search issues: %s", query)
+            log_rate_limit(self.log, github)
 
-        self.log.debug("Ran search issues: %s", query)
-        log_rate_limit(self.log, github)
-        return prs
+        for key in keys:
+            (proj, num, sha) = key
+            project = self.source.getProject(proj)
+            change = self._getChange(project, int(num), patchset=sha)
+            changes.append(change)
+
+        return changes
 
     def _updateChange(self, change, history=None):
-
         # If this change is already in the history, we have a cyclic
         # dependency loop and we do not need to update again, since it
         # was done in a previous frame.
@@ -770,10 +789,10 @@
         change.reviews = self.getPullReviews(change.project,
                                              change.number)
         change.labels = change.pr.get('labels')
-        change.body = change.pr.get('body')
-        # ensure body is at least an empty string
-        if not change.body:
-            change.body = ''
+        # ensure message is at least an empty string
+        change.message = change.pr.get('body') or ''
+        change.updated_at = self._ghTimestampToDate(
+            change.pr.get('updated_at'))
 
         if history is None:
             history = []
@@ -781,38 +800,7 @@
             history = history[:]
         history.append((change.project.name, change.number))
 
-        needs_changes = []
-
-        # Get all the PRs this may depend on
-        for pr in self._getDependsOnFromPR(change.body):
-            proj = pr.get('base').get('repo').get('full_name')
-            pull = pr.get('number')
-            self.log.debug("Updating %s: Getting dependent "
-                           "pull request %s/%s" %
-                           (change, proj, pull))
-            project = self.source.getProject(proj)
-            dep = self._getChange(project, pull,
-                                  patchset=pr.get('head').get('sha'),
-                                  history=history)
-            if (not dep.is_merged) and dep not in needs_changes:
-                needs_changes.append(dep)
-
-        change.needs_changes = needs_changes
-
-        needed_by_changes = []
-        for pr in self._getNeededByFromPR(change):
-            proj = pr.get('base').get('repo').get('full_name')
-            pull = pr.get('number')
-            self.log.debug("Updating %s: Getting needed "
-                           "pull request %s/%s" %
-                           (change, proj, pull))
-            project = self.source.getProject(proj)
-            dep = self._getChange(project, pull,
-                                  patchset=pr.get('head').get('sha'),
-                                  history=history)
-            if not dep.is_merged:
-                needed_by_changes.append(dep)
-        change.needed_by_changes = needed_by_changes
+        self.sched.onChangeUpdated(change)
 
         return change
 
diff --git a/zuul/driver/github/githubmodel.py b/zuul/driver/github/githubmodel.py
index ffd1c3f..0731dd7 100644
--- a/zuul/driver/github/githubmodel.py
+++ b/zuul/driver/github/githubmodel.py
@@ -37,7 +37,8 @@
         self.labels = []
 
     def isUpdateOf(self, other):
-        if (hasattr(other, 'number') and self.number == other.number and
+        if (self.project == other.project and
+            hasattr(other, 'number') and self.number == other.number and
             hasattr(other, 'patchset') and self.patchset != other.patchset and
             hasattr(other, 'updated_at') and
             self.updated_at > other.updated_at):
diff --git a/zuul/driver/github/githubsource.py b/zuul/driver/github/githubsource.py
index 1e7e07a..33f8f7c 100644
--- a/zuul/driver/github/githubsource.py
+++ b/zuul/driver/github/githubsource.py
@@ -12,6 +12,8 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import re
+import urllib
 import logging
 import time
 import voluptuous as v
@@ -44,6 +46,8 @@
         if not change.number:
             # Not a pull request, considering merged.
             return True
+        # We don't need to perform another query because the API call
+        # to perform the merge will ensure this is updated.
         return change.is_merged
 
     def canMerge(self, change, allow_needs):
@@ -61,6 +65,38 @@
     def getChange(self, event, refresh=False):
         return self.connection.getChange(event, refresh)
 
+    change_re = re.compile(r"/(.*?)/(.*?)/pull/(\d+)[\w]*")
+
+    def getChangeByURL(self, url):
+        try:
+            parsed = urllib.parse.urlparse(url)
+        except ValueError:
+            return None
+        m = self.change_re.match(parsed.path)
+        if not m:
+            return None
+        org = m.group(1)
+        proj = m.group(2)
+        try:
+            num = int(m.group(3))
+        except ValueError:
+            return None
+        pull = self.connection.getPull('%s/%s' % (org, proj), int(num))
+        if not pull:
+            return None
+        proj = pull.get('base').get('repo').get('full_name')
+        project = self.getProject(proj)
+        change = self.connection._getChange(
+            project, num,
+            patchset=pull.get('head').get('sha'))
+        return change
+
+    def getChangesDependingOn(self, change, projects):
+        return self.connection.getChangesDependingOn(change, projects)
+
+    def getCachedChanges(self):
+        return self.connection._change_cache.values()
+
     def getProject(self, name):
         p = self.connection.getProject(name)
         if not p:
diff --git a/zuul/driver/zuul/__init__.py b/zuul/driver/zuul/__init__.py
index 0f6ec7d..e381137 100644
--- a/zuul/driver/zuul/__init__.py
+++ b/zuul/driver/zuul/__init__.py
@@ -90,7 +90,18 @@
         if not hasattr(change, 'needed_by_changes'):
             self.log.debug("  %s does not support dependencies" % type(change))
             return
-        for needs in change.needed_by_changes:
+
+        # This is very inefficient, especially on systems with large
+        # numbers of github installations.  This can be improved later
+        # with persistent storage of dependency information.
+        needed_by_changes = set(change.needed_by_changes)
+        for source in self.sched.connections.getSources():
+            self.log.debug("  Checking source: %s", source)
+            needed_by_changes.update(
+                source.getChangesDependingOn(change, None))
+        self.log.debug("  Following changes: %s", needed_by_changes)
+
+        for needs in needed_by_changes:
             self._createParentChangeEnqueuedEvent(needs, pipeline)
 
     def _createParentChangeEnqueuedEvent(self, change, pipeline):
diff --git a/zuul/executor/client.py b/zuul/executor/client.py
index 06c2087..b21a290 100644
--- a/zuul/executor/client.py
+++ b/zuul/executor/client.py
@@ -245,7 +245,7 @@
         for change in dependent_changes:
             # We have to find the project this way because it may not
             # be registered in the tenant (ie, a foreign project).
-            source = self.sched.connections.getSourceByHostname(
+            source = self.sched.connections.getSourceByCanonicalHostname(
                 change['project']['canonical_hostname'])
             project = source.getProject(change['project']['name'])
             if project not in projects:
diff --git a/zuul/executor/server.py b/zuul/executor/server.py
index 5a710a6..a8ab8c4 100644
--- a/zuul/executor/server.py
+++ b/zuul/executor/server.py
@@ -44,7 +44,8 @@
 BUFFER_LINES_FOR_SYNTAX = 200
 COMMANDS = ['stop', 'pause', 'unpause', 'graceful', 'verbose',
             'unverbose', 'keep', 'nokeep']
-DEFAULT_FINGER_PORT = 79
+DEFAULT_FINGER_PORT = 7900
+BLACKLISTED_ANSIBLE_CONNECTION_TYPES = ['network_cli']
 
 
 class StopException(Exception):
@@ -347,6 +348,8 @@
             pass
         self.known_hosts = os.path.join(ssh_dir, 'known_hosts')
         self.inventory = os.path.join(self.ansible_root, 'inventory.yaml')
+        self.setup_inventory = os.path.join(self.ansible_root,
+                                            'setup-inventory.yaml')
         self.logging_json = os.path.join(self.ansible_root, 'logging.json')
         self.playbooks = []  # The list of candidate playbooks
         self.playbook = None  # A pointer to the candidate we have chosen
@@ -493,6 +496,26 @@
                 shutil.copy(os.path.join(library_path, fn), target_dir)
 
 
+def make_setup_inventory_dict(nodes):
+
+    hosts = {}
+    for node in nodes:
+        if (node['host_vars']['ansible_connection'] in
+            BLACKLISTED_ANSIBLE_CONNECTION_TYPES):
+            continue
+
+        for name in node['name']:
+            hosts[name] = node['host_vars']
+
+    inventory = {
+        'all': {
+            'hosts': hosts,
+        }
+    }
+
+    return inventory
+
+
 def make_inventory_dict(nodes, groups, all_vars):
 
     hosts = {}
@@ -1157,8 +1180,13 @@
             result_data_file=self.jobdir.result_data_file)
 
         nodes = self.getHostList(args)
+        setup_inventory = make_setup_inventory_dict(nodes)
         inventory = make_inventory_dict(nodes, args['groups'], all_vars)
 
+        with open(self.jobdir.setup_inventory, 'w') as setup_inventory_yaml:
+            setup_inventory_yaml.write(
+                yaml.safe_dump(setup_inventory, default_flow_style=False))
+
         with open(self.jobdir.inventory, 'w') as inventory_yaml:
             inventory_yaml.write(
                 yaml.safe_dump(inventory, default_flow_style=False))
@@ -1423,6 +1451,7 @@
             verbose = '-v'
 
         cmd = ['ansible', '*', verbose, '-m', 'setup',
+               '-i', self.jobdir.setup_inventory,
                '-a', 'gather_subset=!all']
 
         result, code = self.runAnsible(
diff --git a/zuul/lib/connections.py b/zuul/lib/connections.py
index 262490a..33c66f9 100644
--- a/zuul/lib/connections.py
+++ b/zuul/lib/connections.py
@@ -14,6 +14,7 @@
 
 import logging
 import re
+from collections import OrderedDict
 
 import zuul.driver.zuul
 import zuul.driver.gerrit
@@ -38,7 +39,7 @@
     log = logging.getLogger("zuul.ConnectionRegistry")
 
     def __init__(self):
-        self.connections = {}
+        self.connections = OrderedDict()
         self.drivers = {}
 
         self.registerDriver(zuul.driver.zuul.ZuulDriver())
@@ -85,7 +86,7 @@
 
     def configure(self, config, source_only=False):
         # Register connections from the config
-        connections = {}
+        connections = OrderedDict()
 
         for section_name in config.sections():
             con_match = re.match(r'^connection ([\'\"]?)(.*)(\1)$',
@@ -154,6 +155,13 @@
         connection = self.connections[connection_name]
         return connection.driver.getSource(connection)
 
+    def getSources(self):
+        sources = []
+        for connection in self.connections.values():
+            if hasattr(connection.driver, 'getSource'):
+                sources.append(connection.driver.getSource(connection))
+        return sources
+
     def getReporter(self, connection_name, config=None):
         connection = self.connections[connection_name]
         return connection.driver.getReporter(connection, config)
@@ -162,7 +170,7 @@
         connection = self.connections[connection_name]
         return connection.driver.getTrigger(connection, config)
 
-    def getSourceByHostname(self, canonical_hostname):
+    def getSourceByCanonicalHostname(self, canonical_hostname):
         for connection in self.connections.values():
             if hasattr(connection, 'canonical_hostname'):
                 if connection.canonical_hostname == canonical_hostname:
diff --git a/zuul/lib/dependson.py b/zuul/lib/dependson.py
new file mode 100644
index 0000000..cd0f6ef
--- /dev/null
+++ b/zuul/lib/dependson.py
@@ -0,0 +1,29 @@
+# Copyright 2018 Red Hat, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import re
+
+
+DEPENDS_ON_RE = re.compile(r"^Depends-On: (.*?)\s*$",
+                           re.MULTILINE | re.IGNORECASE)
+
+
+def find_dependency_headers(message):
+    # Search for Depends-On headers
+    dependencies = []
+    for match in DEPENDS_ON_RE.findall(message):
+        if match in dependencies:
+            continue
+        dependencies.append(match)
+    return dependencies
diff --git a/zuul/lib/log_streamer.py b/zuul/lib/log_streamer.py
index c778812..f96f442 100644
--- a/zuul/lib/log_streamer.py
+++ b/zuul/lib/log_streamer.py
@@ -157,12 +157,11 @@
     Class implementing log streaming over the finger daemon port.
     '''
 
-    def __init__(self, user, host, port, jobdir_root):
+    def __init__(self, host, port, jobdir_root):
         self.log = logging.getLogger('zuul.log_streamer')
         self.log.debug("LogStreamer starting on port %s", port)
         self.server = LogStreamerServer((host, port),
                                         RequestHandler,
-                                        user=user,
                                         jobdir_root=jobdir_root)
 
         # We start the actual serving within a thread so we can return to
diff --git a/zuul/lib/streamer_utils.py b/zuul/lib/streamer_utils.py
index 43bc286..3d2d561 100644
--- a/zuul/lib/streamer_utils.py
+++ b/zuul/lib/streamer_utils.py
@@ -74,7 +74,7 @@
     address_family = socket.AF_INET6
 
     def __init__(self, *args, **kwargs):
-        self.user = kwargs.pop('user')
+        self.user = kwargs.pop('user', None)
         self.pid_file = kwargs.pop('pid_file', None)
         socketserver.ThreadingTCPServer.__init__(self, *args, **kwargs)
 
diff --git a/zuul/manager/__init__.py b/zuul/manager/__init__.py
index d205afc..b8a280f 100644
--- a/zuul/manager/__init__.py
+++ b/zuul/manager/__init__.py
@@ -12,9 +12,11 @@
 
 import logging
 import textwrap
+import urllib
 
 from zuul import exceptions
 from zuul import model
+from zuul.lib.dependson import find_dependency_headers
 
 
 class DynamicChangeQueueContextManager(object):
@@ -343,6 +345,32 @@
         self.dequeueItem(item)
         self.reportStats(item)
 
+    def updateCommitDependencies(self, change, change_queue):
+        # Search for Depends-On headers and find appropriate changes
+        self.log.debug("  Updating commit dependencies for %s", change)
+        change.refresh_deps = False
+        dependencies = []
+        seen = set()
+        for match in find_dependency_headers(change.message):
+            self.log.debug("  Found Depends-On header: %s", match)
+            if match in seen:
+                continue
+            seen.add(match)
+            try:
+                url = urllib.parse.urlparse(match)
+            except ValueError:
+                continue
+            source = self.sched.connections.getSourceByCanonicalHostname(
+                url.hostname)
+            if not source:
+                continue
+            self.log.debug("  Found source: %s", source)
+            dep = source.getChangeByURL(match)
+            if dep and (not dep.is_merged) and dep not in dependencies:
+                self.log.debug("  Adding dependency: %s", dep)
+                dependencies.append(dep)
+        change.commit_needs_changes = dependencies
+
     def provisionNodes(self, item):
         jobs = item.findJobsToRequest()
         if not jobs:
diff --git a/zuul/manager/dependent.py b/zuul/manager/dependent.py
index 5aef453..20b376d 100644
--- a/zuul/manager/dependent.py
+++ b/zuul/manager/dependent.py
@@ -95,12 +95,29 @@
     def enqueueChangesBehind(self, change, quiet, ignore_requirements,
                              change_queue):
         self.log.debug("Checking for changes needing %s:" % change)
-        to_enqueue = []
-        source = change.project.source
         if not hasattr(change, 'needed_by_changes'):
             self.log.debug("  %s does not support dependencies" % type(change))
             return
-        for other_change in change.needed_by_changes:
+
+        # for project in change_queue, project.source get changes, then dedup.
+        sources = set()
+        for project in change_queue.projects:
+            sources.add(project.source)
+
+        seen = set(change.needed_by_changes)
+        needed_by_changes = change.needed_by_changes[:]
+        for source in sources:
+            self.log.debug("  Checking source: %s", source)
+            for c in source.getChangesDependingOn(change,
+                                                  change_queue.projects):
+                if c not in seen:
+                    seen.add(c)
+                    needed_by_changes.append(c)
+
+        self.log.debug("  Following changes: %s", needed_by_changes)
+
+        to_enqueue = []
+        for other_change in needed_by_changes:
             with self.getChangeQueue(other_change) as other_change_queue:
                 if other_change_queue != change_queue:
                     self.log.debug("  Change %s in project %s can not be "
@@ -108,6 +125,7 @@
                                    (other_change, other_change.project,
                                     change_queue))
                     continue
+            source = other_change.project.source
             if source.canMerge(other_change, self.getSubmitAllowNeeds()):
                 self.log.debug("  Change %s needs %s and is ready to merge" %
                                (other_change, change))
@@ -145,10 +163,12 @@
         return True
 
     def checkForChangesNeededBy(self, change, change_queue):
-        self.log.debug("Checking for changes needed by %s:" % change)
-        source = change.project.source
         # Return true if okay to proceed enqueing this change,
         # false if the change should not be enqueued.
+        self.log.debug("Checking for changes needed by %s:" % change)
+        if (hasattr(change, 'commit_needs_changes') and
+            (change.refresh_deps or change.commit_needs_changes is None)):
+            self.updateCommitDependencies(change, change_queue)
         if not hasattr(change, 'needs_changes'):
             self.log.debug("  %s does not support dependencies" % type(change))
             return True
@@ -180,7 +200,8 @@
                     self.log.debug("  Needed change is already ahead "
                                    "in the queue")
                     continue
-                if source.canMerge(needed_change, self.getSubmitAllowNeeds()):
+                if needed_change.project.source.canMerge(
+                        needed_change, self.getSubmitAllowNeeds()):
                     self.log.debug("  Change %s is needed" % needed_change)
                     if needed_change not in changes_needed:
                         changes_needed.append(needed_change)
diff --git a/zuul/manager/independent.py b/zuul/manager/independent.py
index 65f5ca0..0c2baf0 100644
--- a/zuul/manager/independent.py
+++ b/zuul/manager/independent.py
@@ -70,6 +70,9 @@
         self.log.debug("Checking for changes needed by %s:" % change)
         # Return true if okay to proceed enqueing this change,
         # false if the change should not be enqueued.
+        if (hasattr(change, 'commit_needs_changes') and
+            (change.refresh_deps or change.commit_needs_changes is None)):
+            self.updateCommitDependencies(change, None)
         if not hasattr(change, 'needs_changes'):
             self.log.debug("  %s does not support dependencies" % type(change))
             return True
diff --git a/zuul/model.py b/zuul/model.py
index 16a701d..bac9e4c 100644
--- a/zuul/model.py
+++ b/zuul/model.py
@@ -2103,11 +2103,28 @@
     def __init__(self, project):
         super(Change, self).__init__(project)
         self.number = None
+        # The gitweb url for browsing the change
         self.url = None
+        # URIs for this change which may appear in depends-on headers.
+        # Note this omits the scheme; i.e., is hostname/path.
+        self.uris = []
         self.patchset = None
 
-        self.needs_changes = []
-        self.needed_by_changes = []
+        # Changes that the source determined are needed due to the
+        # git DAG:
+        self.git_needs_changes = []
+        self.git_needed_by_changes = []
+
+        # Changes that the source determined are needed by backwards
+        # compatible processing of Depends-On headers (Gerrit only):
+        self.compat_needs_changes = []
+        self.compat_needed_by_changes = []
+
+        # Changes that the pipeline manager determined are needed due
+        # to Depends-On headers (all drivers):
+        self.commit_needs_changes = None
+        self.refresh_deps = False
+
         self.is_current_patchset = True
         self.can_merge = False
         self.is_merged = False
@@ -2116,6 +2133,11 @@
         self.status = None
         self.owner = None
 
+        # This may be the commit message, or it may be a cover message
+        # in the case of a PR.  Either way, it's the place where we
+        # look for depends-on headers.
+        self.message = None
+
         self.source_event = None
 
     def _id(self):
@@ -2129,8 +2151,18 @@
             return True
         return False
 
+    @property
+    def needs_changes(self):
+        return (self.git_needs_changes + self.compat_needs_changes +
+                self.commit_needs_changes)
+
+    @property
+    def needed_by_changes(self):
+        return (self.git_needed_by_changes + self.compat_needed_by_changes)
+
     def isUpdateOf(self, other):
-        if ((hasattr(other, 'number') and self.number == other.number) and
+        if (self.project == other.project and
+            (hasattr(other, 'number') and self.number == other.number) and
             (hasattr(other, 'patchset') and
              self.patchset is not None and
              other.patchset is not None and
diff --git a/zuul/scheduler.py b/zuul/scheduler.py
index c3f2f23..a2e3b6e 100644
--- a/zuul/scheduler.py
+++ b/zuul/scheduler.py
@@ -1088,3 +1088,25 @@
         for pipeline in tenant.layout.pipelines.values():
             pipelines.append(pipeline.formatStatusJSON(websocket_url))
         return json.dumps(data)
+
+    def onChangeUpdated(self, change):
+        """Remove stale dependency references on change update.
+
+        When a change is updated with a new patchset, other changes in
+        the system may still have a reference to the old patchset in
+        their dependencies.  Search for those (across all sources) and
+        mark that their dependencies are out of date.  This will cause
+        them to be refreshed the next time the queue processor
+        examines them.
+        """
+
+        self.log.debug("Change %s has been updated, clearing dependent "
+                       "change caches", change)
+        for source in self.connections.getSources():
+            for other_change in source.getCachedChanges():
+                if other_change.commit_needs_changes is None:
+                    continue
+                for dep in other_change.commit_needs_changes:
+                    if change.isUpdateOf(dep):
+                        other_change.refresh_deps = True
+        change.refresh_deps = True
diff --git a/zuul/source/__init__.py b/zuul/source/__init__.py
index 0396aff..00dfc9c 100644
--- a/zuul/source/__init__.py
+++ b/zuul/source/__init__.py
@@ -52,6 +52,29 @@
         """Get the change representing an event."""
 
     @abc.abstractmethod
+    def getChangeByURL(self, url):
+        """Get the change corresponding to the supplied URL.
+
+        The URL may may not correspond to this source; if it doesn't,
+        or there is no change at that URL, return None.
+
+        """
+
+    @abc.abstractmethod
+    def getChangesDependingOn(self, change, projects):
+        """Return changes which depend on changes at the supplied URIs.
+
+        Search this source for changes which depend on the supplied
+        change.  Generally the Change.uris attribute should be used to
+        perform the search, as it contains a list of URLs without the
+        scheme which represent a single change
+
+        If the projects argument is None, search across all known
+        projects.  If it is supplied, the search may optionally be
+        restricted to only those projects.
+        """
+
+    @abc.abstractmethod
     def getProjectOpenChanges(self, project):
         """Get the open changes for a project."""