Warn when git cl upload might be overwriting a newer patchset.

git_cl.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Copyright (C) 2008 Evan Martin <martine@danga.com>
 
 """A git-command for integrating reviews on Rietveld."""
 
 import json
@@ skipping 1267 matching lines @@
   if not options.bypass_hooks:
     hook_results = cl.RunHook(committing=False,
                               may_prompt=not options.force,
                               verbose=options.verbose,
                               change=change)
     if not hook_results.should_continue():
       return 1
     if not options.reviewers and hook_results.reviewers:
       options.reviewers = hook_results.reviewers
 
+  if cl.GetIssue():
+    latest_patchset = cl.GetMostRecentPatchset(cl.GetIssue())
+    local_patchset = cl.GetPatchset()
+    if local_patchset < latest_patchset:

[M-A Ruel, 2013/03/19 01:26:45]

The problem here is that you are comparing patchset ids and not patchset
numbers, and the ids are not guaranteed to be monotonically increasing.

[koz (OOO until 15th September), 2013/03/19 01:29:16]

Oh, they aren't? What if we change '<' to '!=' then, so the warning becomes
about uploading a change to an issue that has been uploaded to from somewhere
else (which is probably basically the same warning).

[M-A Ruel, 2013/04/02 20:08:54]

Yes please do.

[koz (OOO until 15th September), 2013/04/02 20:40:04]

Done.

+      print ('The last upload made from this repository was patchset #%d but '
+            'the most recent patchset on the server is #%d.'
+            % (local_patchset, latest_patchset))
+      ask_for_data('About to upload; enter to confirm.')
+
   print_stats(options.similarity, options.find_copies, args)
   if settings.GetIsGerrit():
     return GerritUpload(options, args, cl)
   return RietveldUpload(options, args, cl)
 
 
 def IsSubmoduleMergeCommit(ref):
   # When submodules are added to the repo, we expect there to be a single
   # non-git-svn merge commit at remote HEAD with a signature comment.
   pattern = '^SVN changes up to revision [0-9]*$'
@@ skipping 585 matching lines @@
              'and retry or visit go/isgaeup.\n%s') % (e.code, str(e)))
 
   # Not a known command. Default to help.
   GenUsage(parser, 'help')
   return CMDhelp(parser, argv)
 
 
 if __name__ == '__main__':
   fix_encoding.fix_encoding()
   sys.exit(main(sys.argv[1:]))