fail gracefully if git rename-branch is called in cog

Bug: 339231299
Change-Id: If88eaa54c579b418516058b1285ce2eb5af6e474
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5540435
Auto-Submit: Yiwei Zhang <yiwzhang@google.com>
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>
Commit-Queue: Josip Sokcevic <sokcevic@chromium.org>

git_rename_branch.py

@@ -12,8 +12,14 @@ import subprocess2
 from git_common import current_branch, run, set_branch_config, branch_config
 from git_common import branch_config_map
 
+import gclient_utils
+
 
 def main(args):
+    if gclient_utils.IsEnvCog():
+        print('rename-branch command is not supported in non-git environment.',
+              file=sys.stderr)
+        return 1
     current = current_branch()
     if current == 'HEAD':
         current = None