Add SVN->Git migration warning to git cl dcommit users.

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 and Gerrit."""
 
 from __future__ import print_function
@@ skipping 4162 matching lines @@
 If your project has a true, writeable git repository, you probably want to run
 'git cl land' instead.
 If your project has a git mirror of an upstream SVN master, you probably need
 to run 'git svn init'.
 
 Using the wrong command might cause your commit to appear to succeed, and the
 review to be closed, without actually landing upstream. If you choose to
 proceed, please verify that the commit lands upstream as expected."""
     print(message)
     ask_for_data('[Press enter to dcommit or ctrl-C to quit]')
+  # TODO(tandrii): kill this post SVN migration with
+  # https://codereview.chromium.org/2076683002
+  print('WARNING: chrome infrastructure is migrating SVN repos to Git.\n'
+        'Please let us know of this project you are committing to:'
+        '    http://crbug.com/600451')
   return SendUpstream(parser, args, 'dcommit')
 
 
 @subcommand.usage('[upstream branch to apply against]')
 def CMDland(parser, args):
   """Commits the current changelist via git."""
   if settings.GetIsGitSvn() or git_footers.get_footer_svn_id():
     print('This appears to be an SVN repository.')
     print('Are you sure you didn\'t mean \'git cl dcommit\'?')
     print('(Ignore if this is the first commit after migrating from svn->git)')
@@ skipping 836 matching lines @@
 if __name__ == '__main__':
   # These affect sys.stdout so do it outside of main() to simplify mocks in
   # unit testing.
   fix_encoding.fix_encoding()
   setup_color.init()
   try:
     sys.exit(main(sys.argv[1:]))
   except KeyboardInterrupt:
     sys.stderr.write('interrupted\n')
     sys.exit(1)