Allow github trigger to match on branches/refs

Change-Id: If33d5566813f08704db2ed6983541eec31c96a55
diff --git a/tests/fixtures/layouts/basic-github.yaml b/tests/fixtures/layouts/basic-github.yaml
index 53f0c0f..709fd02 100644
--- a/tests/fixtures/layouts/basic-github.yaml
+++ b/tests/fixtures/layouts/basic-github.yaml
@@ -8,6 +8,7 @@
             - opened
             - changed
             - reopened
+          branch: '^master$'
         - event: pull_request
           action: comment
           comment: 'test me'