Add GetRemoteMasterHash() function to git_utils.py.

slave/skia_slave_scripts/utils/force_update_checkout.py

 #!/usr/bin/env python
 # Copyright (c) 2014 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.
 
 
 """Forcibly update the local checkout."""
 
 
 
 import os
 import shlex
 import sys
 
 import misc
 
 sys.path.append(os.path.join(misc.BUILDBOT_PATH, 'site_config'))
 sys.path.append(os.path.join(misc.BUILDBOT_PATH, 'third_party',
                              'chromium_buildbot', 'scripts'))
 
-from git_utils import GIT
 import gclient_utils
+import git_utils
 import shell_utils
 import skia_vars
 
 
 BUILDBOT_GIT_URL = skia_vars.GetGlobalVariable('buildbot_git_url')
 GOT_REVISION_PATTERN = 'Skiabot scripts updated to %s'
 
 
 def force_update():
   with misc.ChDir(os.path.join(misc.BUILDBOT_PATH, os.pardir)):
     # Be sure that we sync to the most recent commit.
     buildbot_revision = None
     try:
-      # TODO(borenet): Make this a function in git_utils. Something like,
-      # "GetRemoteMasterHash"
-      output = shell_utils.run([GIT, 'ls-remote',
-                                BUILDBOT_GIT_URL, '--verify',
-                                'refs/heads/master'])
+      output = git_utils.GetRemoteMasterHash(BUILDBOT_GIT_URL)
       if output:
         buildbot_revision = shlex.split(output)[0]
     except shell_utils.CommandFailedException:
       pass
     if not buildbot_revision:
       buildbot_revision = 'origin/master'
 
     gclient_utils.Sync(revisions=[('buildbot', buildbot_revision)],
                        verbose=True, force=True)
     got_revision = gclient_utils.GetCheckedOutHash()
     print GOT_REVISION_PATTERN % got_revision
 
     return gclient_utils.GetCheckedOutHash()
 
 
 if __name__ == '__main__':
   force_update()