contrib: Add a simple tool for pushing to named reviewers

This is a sort of simplified version of git-review[1] for users like
myself who don't mind most git command line tools, and therefore don't
feel the need to switch to a full git-review workflow, but still don't
like the HEAD:refs/for/master%r=user@domain.com syntax for specifying
reviewers during a push.

Reviewer aliases can be specified in a git config file:

[reviewer]
  sop = sop@google.com

$ git push-reviewer --dry-run sop
git push origin HEAD:refs/for/master%r=sop@google.com

[1] http://www.mediawiki.org/wiki/Gerrit/git-review

Change-Id: Ib0c8d609ed9eab17b71ddb13da417a9bfd013611

contrib/git-push-review

@@ -0,0 +1,88 @@
+#!/usr/bin/python
+# Copyright (C) 2014 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import print_function
+
+import argparse
+import collections
+import os
+import subprocess
+import sys
+
+
+def get_config(name):
+  args = ['git', 'config', '--get', name]
+  p = subprocess.Popen(args, stdout=subprocess.PIPE)
+  out, _ = p.communicate()
+  ret = p.poll()
+  if ret not in (0, 1):
+    raise subprocess.CalledProcessError(ret, ' '.join(args), output=out)
+  return out.strip()
+
+
+def deref(name):
+  p = subprocess.Popen(
+      ['git', 'rev-parse', '--symbolic-full-name', name],
+      stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+  out, _ = p.communicate()
+  return out.strip()
+
+
+def main(argv):
+  p = argparse.ArgumentParser(description='Push changes to Gerrit for review')
+  p.add_argument('-r', '--remote', default='', metavar='REMOTE',
+                 help='remote name or URL to push to')
+  p.add_argument('-b', '--branch', default='', metavar='BRANCH',
+                 help='remote branch name, refs/for/BRANCH')
+  p.add_argument('reviewers', nargs='*', metavar='REVIEWER',
+                 help='reviewer names or aliases')
+  p.add_argument('-t', '--topic', default='', metavar='TOPIC',
+                 help='topic for new changes')
+  p.add_argument('--dry-run', action='store_true',
+                 help='dry run, print git command and exit')
+  args = p.parse_args()
+
+  if not args.remote or not args.branch:
+    hp = 'refs/heads/'
+    upstream = deref('HEAD')
+    while upstream.startswith(hp):
+      upstream = deref(upstream[len(hp):] + '@{u}')
+
+    rp = 'refs/remotes/'
+    if upstream.startswith(rp):
+      def_remote, def_branch = upstream[len(rp):].split('/', 1)
+    else:
+      def_remote, def_branch = 'origin', 'master'
+    args.remote = args.remote or def_remote
+    args.branch = args.branch or def_branch
+
+  opts = collections.defaultdict(list)
+  opts['r'].extend((get_config('reviewer.' + r) or r) for r in args.reviewers)
+  if args.topic:
+    opts['topic'].append(args.topic)
+  opts_str = ','.join('%s=%s' % (k, v) for k in opts for v in opts[k])
+  if opts_str:
+    opts_str = '%' + opts_str
+
+  git_args = ['git', 'push', args.remote,
+              'HEAD:refs/for/%s%s' % (args.branch, opts_str)]
+  if args.dry_run:
+    print(' '.join(git_args))
+    return 0
+  os.execvp('git', git_args)
+
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv))