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
diff --git a/doc/source/connections.rst b/doc/source/connections.rst
index 298100a..34b8f94 100644
--- a/doc/source/connections.rst
+++ b/doc/source/connections.rst
@@ -42,6 +42,13 @@
   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
 ~~~~~~~~~~~~~~~~~~~~