Fix stats output to be always the same and coherent with what is committed.

tests/git_cl_test.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.
 
 """Unit tests for git_cl.py."""
 
 import os
 import StringIO
 import stat
@@ skipping 174 matching lines @@
       ((['git', 'config', 'branch.working.rietveldserver'],),
          'codereview.example.com'),
       (('GitClHooksBypassedCommit',
         'Issue https://codereview.example.com/12345 bypassed hook when '
         'committing'), None),
   ]
 
   @classmethod
   def _dcommit_calls_3(cls):
     return [
-      ((['git', 'diff', '--stat', 'refs/remotes/origin/master',
-         'refs/heads/working'],),
+      ((['git', 'diff', '--no-ext-diff', '--stat', '--find-copies-harder',
+         'refs/remotes/origin/master', 'refs/heads/working'],),
        (' PRESUBMIT.py |    2 +-\n'
         ' 1 files changed, 1 insertions(+), 1 deletions(-)\n')),
       (('About to commit; enter to confirm.',), None),
       ((['git', 'show-ref', '--quiet', '--verify',
          'refs/heads/git-cl-commit'],),
        (('', None), 0)),
       ((['git', 'branch', '-D', 'git-cl-commit'],), ''),
       ((['git', 'show-ref', '--quiet', '--verify',
          'refs/heads/git-cl-cherry-pick'],), ''),
       ((['git', 'rev-parse', '--show-cdup'],), '\n'),
@@ skipping 251 matching lines @@
         ((['git', 'config', 'rietveld.viewvc-url'],), ''),
         (('ViewVC URL:',), ''),
         # DownloadHooks(True)
         ((commit_msg_path, os.X_OK,), True),
         ]
     git_cl.main(['config'])
 
 
 if __name__ == '__main__':
   unittest.main()