Revert of Revert "Add (another) argument to break git locks in gclient."

gclient.py

Index: gclient.py
diff --git a/gclient.py b/gclient.py
index 5a40321f19181f9fc4c7c2d0475533f31c9dd132..a31491e893eb6ea2e9a1211c04c3ae4ccfe58165 100755
--- a/gclient.py
+++ b/gclient.py
@@ -2050,6 +2050,11 @@
                     help='Don\'t bootstrap from Google Storage.')
   parser.add_option('--ignore_locks', action='store_true',
                     help='GIT ONLY - Ignore cache locks.')
+  parser.add_option('--break_repo_locks', action='store_true',
+                    help='GIT ONLY - Forcibly remove repo locks (e.g. '
+                      'index.lock). This should only be used if you know for '
+                      'certain that this invocation of gclient is the only '
+                      'thing operating on the git repos (e.g. on a bot).')
   parser.add_option('--lock_timeout', type='int', default=5000,
                     help='GIT ONLY - Deadline (in seconds) to wait for git '
                          'cache lock to become available. Default is %default.')