error if repo command is called in Cog environment

Bug: 345486495
Change-Id: I0a03d210b5662828f65dc45bd0121c33bd6480f2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5608833
Auto-Submit: Yiwei Zhang <yiwzhang@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@chromium.org>
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>

repo

@@ -15,6 +15,8 @@ from pathlib import Path
 import subprocess
 import sys
 
+import gclient_utils
+
 # Some useful paths.
 DEPOT_TOOLS_DIR = Path(__file__).resolve().parent
 UPDATE_DEPOT_TOOLS = DEPOT_TOOLS_DIR / 'update_depot_tools'
@@ -45,6 +47,10 @@ def _UpdateDepotTools():
 
 
 def main(argv):
+    if gclient_utils.IsEnvCog():
+        print('"repo" is not supported in non-git environment.',
+              file=sys.stderr)
+        return 1
     # This is a bit hacky, but should be "good enough".  If repo itself gains
     # support for sync hooks, we could switch to that.
     if argv and argv[0] == 'sync':