Add strip_branch_ref compat option

This adds a compatability option to deal with a Gerrit behavior
change between 2.11 and 2.13.

Change-Id: I012485065e0fd8692e4f2ef787dd0a62be303314

doc/source/connections.rst

@@ -42,6 +42,13 @@ Create a connection with gerrit.
   Optional: Keepalive timeout, 0 means no keepalive.
   ``keepalive=60``
 
+**strip_branch_ref**
+  Optional: Earlier versions of Gerrit reported branch refs in the
+  form "master" and later forms as "refs/heads/master".  Set this to 1
+  to enable compatibility with the earlier form by stripping the
+  "refs/heads/" portion of the ref.
+  ``strip_branch_ref=1``
+
 Gerrit Configuration
 ~~~~~~~~~~~~~~~~~~~~
 

zuul/connection/gerrit.py

@@ -75,6 +75,9 @@ class GerritEventConnector(threading.Thread):
         if refupdate:
             event.project_name = refupdate.get('project')
             event.ref = refupdate.get('refName')
+            if (self.connection.strip_branch_ref and
+                event.ref.startswith('refs/heads/')):
+                event.ref = event.ref[len('refs/heads/'):]
             event.oldrev = refupdate.get('oldRev')
             event.newrev = refupdate.get('newRev')
         # Map the event types to a field name holding a Gerrit
@@ -231,6 +234,8 @@ class GerritConnection(BaseConnection):
         self.port = int(self.connection_config.get('port', 29418))
         self.keyfile = self.connection_config.get('sshkey', None)
         self.keepalive = int(self.connection_config.get('keepalive', 60))
+        self.strip_branch_ref = bool(self.connection_config.get(
+            'strip_branch_ref'))
         self.watcher_thread = None
         self.event_queue = None
         self.client = None