Make git cl upload correctly track upstream refs when uploading to Gerrit

git_cl.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Copyright (C) 2008 Evan Martin <martine@danga.com>
 
 """A git-command for integrating reviews on Rietveld."""
 
 from distutils.version import LooseVersion
@@ skipping 1684 matching lines @@
     print 'git-cl: Added Change-Id to commit message.'
   else:
     print >> sys.stderr, 'ERROR: Gerrit commit-msg hook not available.'
 
 
 def GerritUpload(options, args, cl, change):
   """upload the current branch to gerrit."""
   # We assume the remote called "origin" is the one we want.
   # It is probably not worthwhile to support different workflows.
   gerrit_remote = 'origin'
-  branch = 'master'
-  if options.target_branch:
-    branch = options.target_branch
+
+  remote, remote_branch = cl.GetRemoteBranch()
+  branch = GetTargetRef(remote, remote_branch, options.target_branch,
+                        pending_prefix='')
 
   change_desc = ChangeDescription(
       options.message or CreateDescriptionFromLog(args))
   if not change_desc.description:
     print "Description is empty; aborting."
     return 1
 
   if options.squash:
     # Try to get the message from a previous upload.
     shadow_branch = 'refs/heads/git_cl_uploads/' + cl.GetBranch()
@@ skipping 1486 matching lines @@
 if __name__ == '__main__':
   # These affect sys.stdout so do it outside of main() to simplify mocks in
   # unit testing.
   fix_encoding.fix_encoding()
   colorama.init()
   try:
     sys.exit(main(sys.argv[1:]))
   except KeyboardInterrupt:
     sys.stderr.write('interrupted\n')
     sys.exit(1)