GitHub file matching support

Allow to configure jobs to run only when certain files are changed.

Github does not list the /COMMIT_MSG in the changed files as gerrit
does. Therefore the matcher now returns False only if the single file is
the /COMMIT_MSG one.

Change-Id: I4fa8a328f2ba430c25377e50e1eff7c45829eba6
diff --git a/tests/fixtures/layouts/files-github.yaml b/tests/fixtures/layouts/files-github.yaml
new file mode 100644
index 0000000..734b945
--- /dev/null
+++ b/tests/fixtures/layouts/files-github.yaml
@@ -0,0 +1,18 @@
+- pipeline:
+    name: check
+    manager: independent
+    trigger:
+      github:
+        - event: pull_request
+          action: opened
+
+- job:
+    name: project-test1
+    files:
+      - '.*-requires'
+
+- project:
+    name: org/project
+    check:
+      jobs:
+        - project-test1