Change --mirror to --bare in gclient_scm.py for cache directories

BUG=339168

Review URL: https://codereview.chromium.org/140553007

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@250547 0039d316-1c4b-4281-b951-d872f2087c98

gclient_scm.py

@@ -770,7 +770,7 @@ class GitWrapper(SCMWrapper):
       if not os.path.exists(os.path.join(folder, 'config')):
         gclient_utils.rmtree(folder)
         cmd = ['clone'] + v + ['-c', 'core.deltaBaseCacheLimit=2g',
-                               '--progress', '--mirror']
+                               '--progress', '--bare']
 
         if use_reference:
           cmd += ['--reference', os.path.abspath(self.checkout_path)]