Fix Gerrit git cl land and add test.

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 and Gerrit."""
 
 from __future__ import print_function
@@ skipping 2288 matching lines @@
       return 1
     detail = self._GetChangeDetail(['CURRENT_REVISION', 'LABELS'])
     if u'Commit-Queue' in detail.get('labels', {}):
       if not force:
         ask_for_data('\nIt seems this repository has a Commit Queue, '
                      'which can test and land changes for you. '
                      'Are you sure you wish to bypass it?\n'
                      'Press Enter to continue, Ctrl+C to abort.')
 
     differs = True
-    last_upload = RunGit(['config', self._GitBranchSetting('gerritsquashhash')],
-                         error_ok=True).strip()
+    last_upload = self._GitGetBranchConfigValue('gerritsquashhash')
     # Note: git diff outputs nothing if there is no diff.
     if not last_upload or RunGit(['diff', last_upload]).strip():
       print('WARNING: some changes from local branch haven\'t been uploaded')
     else:
       if detail['current_revision'] == last_upload:
         differs = False
       else:
         print('WARNING: local branch contents differ from latest uploaded '
               'patchset')
     if differs:
@@ skipping 2896 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()
   setup_color.init()
   try:
     sys.exit(main(sys.argv[1:]))
   except KeyboardInterrupt:
     sys.stderr.write('interrupted\n')
     sys.exit(1)