Added git footers tool to parse conventional metadata from git commits

git_footers.py

Index: git_footers.py
diff --git a/git_footers.py b/git_footers.py
new file mode 100755
index 0000000000000000000000000000000000000000..12299f7d7a2a07ecae00520c35b4f4786fc3312c
--- /dev/null
+++ b/git_footers.py
@@ -0,0 +1,70 @@
+#!/usr/bin/env python
+# Copyright 2014 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.
+
+import argparse
+import re
+import sys
+
+from collections import defaultdict
+
+import git_common as git
+
+FOOTER_PATTERN = re.compile(r'^\s*([\w-]+): (.*)$')
+
+def normalize_name(header):
+  return '-'.join([ word.title() for word in header.strip().split('-') ])
+
+
+def parse_footer(line):
+  match = FOOTER_PATTERN.match(line)
+  if match:
+    return (match.group(1), match.group(2))
+  else:
+    return None
+
+
+def parse_footers(log):

[iannucci, 2014/08/30 00:24:19]

this isn't really a log, it's a commit message. name msg and docstring?

+  log_lines = []
+  for line in reversed(log.splitlines()):
+    if line == '' or line.isspace():
+      break
+    log_lines.append(line)
+
+  footers = map(parse_footer, log_lines)
+  if not all(footers):
+    return defaultdict(list)
+
+  footer_map = defaultdict(list)
+  for (k, v) in footers:
+    footer_map[normalize_name(k)].append(v.strip())
+
+  return footer_map
+
+
+def main(args):
+  parser = argparse.ArgumentParser(
+    formatter_class=argparse.ArgumentDefaultsHelpFormatter
+  )
+  parser.add_argument('ref')
+  parser.add_argument('--key', metavar='KEY',
+                      help='Get all values for the given header, one per line '
+                           '(case insensitive)')

[iannucci, 2014/08/30 00:24:19]

could we also add a special --position, --position_ref, --position_num, which
do:
  * if there's a Cr-Commit-Position, return that (or the parsed ref/num portion)
  * if there's a git-svn-id, determine the effective ref by:
    * if url ends with /chrome/trunk/src 
      * ref -> refs/heads/master
      * num -> svn revision
    * if url ends with /chrome/branches/..../src
      * ref -> refs/branch-heads/....
      * num -> None

+
+  opts = parser.parse_args(args)
+
+  log = git.run('log', '-1', opts.ref)

[iannucci, 2014/08/30 00:24:19]

suggest formatting this using --format=%B

+  footers = parse_footers(log)
+
+  if opts.key:
+    for v in footers.get(normalize_name(opts.key), []):
+      print v
+  else:
+    for k in footers.keys():
+      for v in footers[k]:
+        print '%s: %s' % (k, v)
+
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv[1:]))