Revert of Revert "Add (another) argument to break git locks in gclient." (patchset #1 id:1 of https://codereview.chromium.org/1865403003/ )

Reason for revert:
This revert breaks /everything/

Original issue's description:
> Revert "Add (another) argument to break git locks in gclient."
> 
> This reverts commit 51797b1d8f24a26aa7f9c23212e06ed2b6cfc0e9.
> 
> BUG=601564
> TBR=iannucci,dpranke,estaab,pgervais
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=299771

TBR=dpranke@google.com,estaab@chromium.org,pgervais@chromium.org,smut@google.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=601564

Review URL: https://codereview.chromium.org/1867843003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@299773 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/gclient.py b/gclient.py
index 5a40321..a31491e 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.')