branch_util: Add a argument to branch-util to skip remote push.

This CL adds an argument to the branch-util subgroup of cbuildbot to
skip pushing to remote repositories completely. This will be used by an
integration test that uses branch_util end-to-end, skipping just the
push-to-remote part.

BUG=chromium:470690
TEST=`cbuildbot --local branch-util --skip-remote-push \
          --branch-name blah --version 7041.0.0`

Change-Id: I73cb1afdcc1daa9ac7ced916f9b5876e7ba7e06a
Reviewed-on: https://chromium-review.googlesource.com/270043
Tested-by: Prathmesh Prabhu <pprabhu@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Commit-Queue: Prathmesh Prabhu <pprabhu@chromium.org>
diff --git a/scripts/cbuildbot.py b/scripts/cbuildbot.py
index c06f441..55b90b2 100644
--- a/scripts/cbuildbot.py
+++ b/scripts/cbuildbot.py
@@ -495,6 +495,10 @@
                           help='Rename a branch to the specified name.')
   group.add_remote_option('--force-create', default=False, action='store_true',
                           help='Overwrites an existing branch.')
+  group.add_remote_option('--skip-remote-push', default=False,
+                          action='store_true',
+                          help='Do not actually push to remote git repos.  '
+                               'Used for end-to-end testing branching.')
 
   parser.add_option_group(group)