fail gracefully if git find-releases is called in cog

Bug: 339231299
Change-Id: I70e02cf053bae635d3db007fc9ef3aa534e6c749
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5539650
Commit-Queue: Josip Sokcevic <sokcevic@chromium.org>
Auto-Submit: Yiwei Zhang <yiwzhang@google.com>
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>

git_find_releases.py

@@ -15,6 +15,7 @@ import optparse
 import re
 import sys
 
+import gclient_utils
 import git_common as git
 
 
@@ -37,6 +38,10 @@ def GetMergesForCommit(sha1):
 
 
 def main(args):
+    if gclient_utils.IsEnvCog():
+        print('find-releases command is not supported in non-git environment.',
+              file=sys.stderr)
+        return 1
     parser = optparse.OptionParser(usage=sys.modules[__name__].__doc__)
     _, args = parser.parse_args(args)