sync-webkit-git: reduce diff-index output

We run diff-index to see if there are any changes we need to pull in,
but we don't need it to print all of those changes.

Review URL: http://codereview.chromium.org/202045

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@25869 0039d316-1c4b-4281-b951-d872f2087c98

tools/sync-webkit-git.py

@@ -75,7 +75,8 @@ def UpdateCurrentCheckoutIfAppropriate():
     print "Run 'git checkout gclient' to put this under control of gclient."
     return
 
-  if subprocess.call(['git', 'diff-index', '--exit-code', 'HEAD']):
+  if subprocess.call(['git', 'diff-index', '--exit-code', '--shortstat',
+	              'HEAD']):
     print "Resetting tree state to new revision."
     subprocess.check_call(['git', 'reset', '--hard'])