Allow blocking git-cache update with a timeout.

I guess I'm the only developer using git-cache, which is sad.
Hopefully these fixes will make it easier to adapt this to developer
usage some time in the FUTURE.

BUG=583420
TEST=Works for me
R=agable@chromium.org,tandrii@chromium.org

Review URL: https://codereview.chromium.org/1650993005

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@298531 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/gclient.py b/gclient.py
index 00bb95d..507721f 100755
--- a/gclient.py
+++ b/gclient.py
@@ -2049,6 +2049,9 @@
                     help='Don\'t bootstrap from Google Storage.')
   parser.add_option('--ignore_locks', action='store_true',
                     help='GIT ONLY - Ignore cache locks.')
+  parser.add_option('--lock_timeout', type='int', default=0,
+                    help='GIT ONLY - Deadline (in seconds) to wait for git '
+                         'cache lock to become available.')
   (options, args) = parser.parse_args(args)
   client = GClient.LoadCurrentConfig(options)