Add `git cl checkout` to checkout by Rietveld issue

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."""
 
 from distutils.version import LooseVersion
@@ skipping 3523 matching lines @@
       stdout = RunCommand(command, cwd=top_dir, env=env)
       if opts.dry_run and stdout:
         return_value = 2
     except dart_format.NotFoundError as e:
       print ('Unable to check dart code formatting. Dart SDK is not in ' +
              'this checkout.')
 
   return return_value
 
 
+@subcommand.usage('<codereview url or issue id>')
+def CMDcheckout(parser, args):
+  """Checks out a branch associated with a given Rietveld issue."""
+  _, args = parser.parse_args(args)
+
+  if len(args) != 1:
+    parser.print_help()
+    return 1
+
+  if re.match(r'\d+', args[0]):
+    target_issue = args[0]
+  elif args[0].startswith('http'):
+    target_issue = re.sub(r'.*/(\d+)/?', r'\1', args[0])
+  else:
+    parser.print_help()
+    return 1
+
+  key_and_issues = [x.split() for x in RunGit(
+      ['config', '--local', '--get-regexp', r'branch\..*\.rietveldissue'])
+      .splitlines()]
+  branches = []
+  for key, issue in key_and_issues:
+    if issue == target_issue:
+      branches.append(re.sub(r'branch\.(.*)\.rietveldissue', r'\1', key))
+
+  if len(branches) == 0:
+    print 'No branch found for issue %s.' % target_issue
+    return 1
+  if len(branches) == 1:
+    RunGit(['checkout', branches[0]])
+  else:
+    print 'Multiple branches match issue %s:' % target_issue
+    for i in range(len(branches)):
+      print '%d: %s' % (i, branches[i])
+    which = raw_input('Choose by index: ')
+    try:
+      RunGit(['checkout', branches[int(which)]])
+    except (IndexError, ValueError):
+      print 'Invalid selection, not checking out any branch.'
+      return 1
+
+  return 0
+
+
 def CMDlol(parser, args):
   # This command is intentionally undocumented.
   print zlib.decompress(base64.b64decode(
       'eNptkLEOwyAMRHe+wupCIqW57v0Vq84WqWtXyrcXnCBsmgMJ+/SSAxMZgRB6NzE'
       'E2ObgCKJooYdu4uAQVffUEoE1sRQLxAcqzd7uK2gmStrll1ucV3uZyaY5sXyDd9'
       'JAnN+lAXsOMJ90GANAi43mq5/VeeacylKVgi8o6F1SC63FxnagHfJUTfUYdCR/W'
       'Ofe+0dHL7PicpytKP750Fh1q2qnLVof4w8OZWNY'))
   return 0
 
 
@@ skipping 42 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()
   colorama.init()
   try:
     sys.exit(main(sys.argv[1:]))
   except KeyboardInterrupt:
     sys.stderr.write('interrupted\n')
     sys.exit(1)