Add some v3 notes

Change-Id: I704ac03ee0669420eb673d145f0bde9f664d2b26
diff --git a/zuul/launcher/server.py b/zuul/launcher/server.py
index 89969cd..7cac5f7 100644
--- a/zuul/launcher/server.py
+++ b/zuul/launcher/server.py
@@ -28,6 +28,11 @@
 import zuul.merger
 
 
+# TODOv3(mordred): put git repos in a hierarchy that includes source
+# hostname, eg: git.openstack.org/openstack/nova.  Also, configure
+# sources to have an alias, so that the review.openstack.org source
+# repos end up in git.openstack.org.
+
 class JobDir(object):
     def __init__(self):
         self.root = tempfile.mkdtemp()
diff --git a/zuul/model.py b/zuul/model.py
index 6588a41..e99c7b9 100644
--- a/zuul/model.py
+++ b/zuul/model.py
@@ -1113,6 +1113,8 @@
 
 
 class NullChange(Changeish):
+    # TODOv3(jeblair): remove this in favor of enqueueing Refs (eg
+    # current master) instead.
     def __repr__(self):
         return '<NullChange for %s>' % (self.project)