Added git footers tool to parse conventional metadata from git commits

BUG=407316

Review URL: https://codereview.chromium.org/521033002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@291777 0039d316-1c4b-4281-b951-d872f2087c98

git-footers

+#!/usr/bin/env bash
+# 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.
+
+# git_footers.py -- Extract the conventional footers associated with a commit.
+
+. $(type -P python_git_runner.sh)

git_footers.py

+#!/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-]+): (.*)$')
+CHROME_COMMIT_POSITION_PATTERN = re.compile(r'^([\w/-]+)@{#(\d+)}$')
+GIT_SVN_ID_PATTERN = re.compile('^([^\s@]+)@(\d+)')
+
+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(message):
+  """Parses a git commit message into a multimap of footers."""
+  footer_lines = []
+  for line in reversed(message.splitlines()):
+    if line == '' or line.isspace():
+      break
+    footer_lines.append(line)
+
+  footers = map(parse_footer, footer_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 get_unique(footers, key):
+  key = normalize_name(key)
+  values = footers[key]
+  assert len(values) <= 1, 'Multiple %s footers' % key
+  if values:
+    return values[0]
+  else:
+    return None
+
+
+def get_position(footers):
+  """Get the chrome commit position from a footer multimap using a heuristic.
+
+  Returns:
+    A tuple of the branch and the position on that branch. For example,
+
+    Cr-Commit-Position: refs/heads/master@{#292272}
+
+    would give the return value ('refs/heads/master', 292272).  If
+    Cr-Commit-Position is not defined, we try to infer the ref and position
+    from git-svn-id. The position number can be None if it was not inferrable.
+  """
+
+  position = get_unique(footers, 'Cr-Commit-Position')
+  if position:
+    match = CHROME_COMMIT_POSITION_PATTERN.match(position)
+    assert match, 'Invalid Cr-Commit-Position value: %s' % position
+    return (match.group(1), match.group(2))
+
+  svn_commit = get_unique(footers, 'git-svn-id')
+  if svn_commit:
+    match = GIT_SVN_ID_PATTERN.match(svn_commit)
+    assert match, 'Invalid git-svn-id value: %s' % svn_commit
+    if re.match('.*/chrome/trunk/src$', match.group(1)):
+      return ('refs/heads/master', match.group(2))
+    branch_match = re.match('.*/chrome/branches/([\w/-]+)/src$', match.group(1))
+    if branch_match:
+      # svn commit numbers do not map to branches.
+      return ('refs/branch-heads/%s' % branch_match.group(1), None)
+
+  raise ValueError('Unable to infer commit position from footers')
+
+
+def main(args):
+  parser = argparse.ArgumentParser(
+    formatter_class=argparse.ArgumentDefaultsHelpFormatter
+  )
+  parser.add_argument('ref')
+
+  g = parser.add_mutually_exclusive_group()
+  g.add_argument('--key', metavar='KEY',
+                 help='Get all values for the given footer name, one per '
+                 'line (case insensitive)')
+  g.add_argument('--position', action='store_true')
+  g.add_argument('--position-ref', action='store_true')
+  g.add_argument('--position-num', action='store_true')
+
+
+  opts = parser.parse_args(args)
+
+  message = git.run('log', '-1', '--format=%B', opts.ref)
+  footers = parse_footers(message)
+
+  if opts.key:
+    for v in footers.get(normalize_name(opts.key), []):
+      print v
+  elif opts.position:
+    pos = get_position(footers)
+    print '%s@{#%s}' % (pos[0], pos[1] or '?')
+  elif opts.position_ref:
+    print get_position(footers)[0]
+  elif opts.position_num:
+    pos = get_position(footers)
+    assert pos[1], 'No valid position for commit'
+    print pos[1]
+  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:]))

man/man1/git-footers.1

+'\" t
+.\"     Title: git-freeze
+.\"    Author: [FIXME: author] [see http://docbook.sf.net/el/author]
+.\" Generator: DocBook XSL Stylesheets v1.76.1 <http://docbook.sf.net/>
+.\"      Date: 09/02/2014
+.\"    Manual: Chromium depot_tools Manual
+.\"    Source: depot_tools c9f28eb
+.\"  Language: English
+.\"
+.TH "GIT\-FREEZE" "1" "09/02/2014" "depot_tools c9f28eb" "Chromium depot_tools Manual"
+.\" -----------------------------------------------------------------
+.\" * Define some portability stuff
+.\" -----------------------------------------------------------------
+.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+.\" http://bugs.debian.org/507673
+.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
+.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+.ie \n(.g .ds Aq \(aq
+.el       .ds Aq '
+.\" -----------------------------------------------------------------
+.\" * set default formatting
+.\" -----------------------------------------------------------------
+.\" disable hyphenation
+.nh
+.\" disable justification (adjust text to left margin only)
+.ad l
+.\" -----------------------------------------------------------------
+.\" * MAIN CONTENT STARTS HERE *
+.\" -----------------------------------------------------------------
+.SH "NAME"
+git-footers \- Extract meta\-information expressed as footers in a commit message\&.
+.SH "SYNOPSIS"
+.sp
+.nf
+\fIgit footers\fR [\-\-key FOOTER] REF
+\fIgit footers\fR [\-\-position | \-\-position\-ref | \-\-position\-num] REF
+.fi
+.sp
+.SH "DESCRIPTION"
+.sp
+git footers extracts information included in commit messages as "footers", which are roughly like HTTP headers except they are at the end\&. For example, a commit might look like:
+.sp
+.if n \{\
+.RS 4
+.\}
+.nf
+This is a fancy commit message\&.
+.fi
+.if n \{\
+.RE
+.\}
+.sp
+.if n \{\
+.RS 4
+.\}
+.nf
+Cr\-Commit\-Position: refs/heads/master@{#292272}
+Tech\-Debt\-Introduced: 17 nanoMSOffices
+.fi
+.if n \{\
+.RE
+.\}
+.sp
+git footers knows how to extract this information\&.
+.sp
+Footers are order\-independent and can appear more than once\&. Thus they are treated as a multimap\&.
+.SH "OPTIONS"
+.sp
+If no options are given, all footers are printed, with their names case\-normalized\&.
+.PP
+\-\-key FOOTER
+.RS 4
+Extract all the headers associated with the given key, and print one per line\&. If there are no footers with this key, produces no output and exits successfully\&.
+.RE
+.PP
+\-\-position
+.RS 4
+Extract the Chrome commit position from the footers\&. This first attempts to get the value of the
+Cr\-Commit\-Position
+footer\&. If that doesn\(cqt exist then it tries a heuristic based on
+Git\-Svn\-Id\&. Output is in one of the following forms:
+.sp
+.if n \{\
+.RS 4
+.\}
+.nf
+refs/heads/master@{#292272}
+refs/branch\-heads/branchname
+.fi
+.if n \{\
+.RE
+.\}
+.RE
+.PP
+\-\-position\-num
+.RS 4
+Extracts and prints the Chrome commit position number only (292272 in the example above)\&. Exits with an error if one cannot be found\&.
+.RE
+.PP
+\-\-position\-ref
+.RS 4
+Extracts and prints the Chrome commit position ref name only (ref/heads/master
+or
+refs/branch\-heads/branchname
+in the example above)\&.
+.RE
+.SH "EXAMPLE"
+.sp
+
+.sp
+.if n \{\
+.RS 4
+.\}
+.nf
+\fB$ git footers HEAD\fR
+Tech\-Debt\-Introduced: \-4 microMSOffices
+Tech\-Debt\-Introduced: 17 microMSOffices
+Cr\-Commit\-Position: refs/heads/master@{#292272}
+\fB$ git footers \-\-key Tech\-Debt\-Introduced HEAD\fR
+\-4 microMSOffices
+17 microMSOffices
+\fB$ git footers \-\-position HEAD\fR
+refs/heads/master@{#292272}
+\fB$ git footers \-\-position\-num HEAD\fR
+292272
+\fB$ git footers \-\-position\-ref HEAD\fR
+refs/heads/master
+.fi
+.if n \{\
+.RE
+.\}
+.sp
+.SH "SEE ALSO"
+.sp
+\fBgit-number\fR(1)
+.SH "CHROMIUM DEPOT_TOOLS"
+.sp
+Part of the chromium \fBdepot_tools\fR(7) suite\&. These tools are meant to assist with the development of chromium and related projects\&. Download the tools from \m[blue]\fBhere\fR\m[]\&\s-2\u[1]\d\s+2\&.
+.SH "NOTES"
+.IP " 1." 4
+here
+.RS 4
+\%https://chromium.googlesource.com/chromium/tools/depot_tools.git
+.RE

man/src/_git-footers_desc.helper.txt

+Extract meta-information expressed as footers in a commit message.

man/src/git-footers.demo.1.sh

+#!/usr/bin/env bash
+. demo_repo.sh
+
+add deleted_file
+add unstaged_deleted_file
+add modified_file
+c 'I commited this and am proud of it.
+
+Cr-Commit-Position: refs/heads/master@{#292272}
+Tech-Debt-Introduced: 17 microMSOffices
+Tech-Debt-Introduced: -4 microMSOffices'
+
+run git footers HEAD
+run git footers --key Tech-Debt-Introduced HEAD
+run git footers --position HEAD
+run git footers --position-num HEAD
+run git footers --position-ref HEAD

man/src/git-footers.txt

+git-freeze(1)
+=============
+
+NAME
+----
+git-footers -
+include::_git-footers_desc.helper.txt[]
+
+SYNOPSIS
+--------
+[verse]
+'git footers' [--key FOOTER] REF
+'git footers' [--position | --position-ref | --position-num] REF
+
+DESCRIPTION
+-----------
+
+`git footers` extracts information included in commit messages as "footers",
+which are roughly like HTTP headers except they are at the end.  For example, a
+commit might look like:
+
+    This is a fancy commit message.
+
+    Cr-Commit-Position: refs/heads/master@{#292272}
+    Tech-Debt-Introduced: 17 nanoMSOffices
+
+`git footers` knows how to extract this information.
+
+Footers are order-independent and can appear more than once. Thus they are
+treated as a multimap.
+
+OPTIONS
+-------
+
+If no options are given, all footers are printed, with their names
+case-normalized.
+
+--key FOOTER::
+  Extract all the headers associated with the given key, and print one per 
+  line. If there are no footers with this key, produces no output and exits
+  successfully.
+
+--position::
+  Extract the Chrome commit position from the footers.  This first attempts
+  to get the value of the `Cr-Commit-Position` footer.  If that doesn't exist
+  then it tries a heuristic based on `Git-Svn-Id`.  Output is in one of the
+  following forms:
+
+    refs/heads/master@{#292272}
+    refs/branch-heads/branchname
+
+--position-num::
+  Extracts and prints the Chrome commit position number only (292272 in the
+  example above).  Exits with an error if one cannot be found.
+
+--position-ref::
+  Extracts and prints the Chrome commit position ref name only 
+  (`ref/heads/master` or `refs/branch-heads/branchname` in the example above).
+
+
+EXAMPLE
+-------
+demo:1[]
+
+SEE ALSO
+--------
+linkgit:git-number[1]
+
+include::_footer.txt[]
+
+// vim: ft=asciidoc:

tests/git_footers_test.py

+#!/usr/bin/env python
+
+"""Tests for git_footers."""
+
+import os
+import sys
+import unittest
+
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+import git_footers
+
+class GitFootersTest(unittest.TestCase):
+  _message = """
+This is my commit message. There are many like it, but this one is mine.
+
+My commit message is my best friend. It is my life. I must master it.
+
+"""
+
+  _position = 'refs/heads/master@{#292272}'
+
+  _position_footer = 'Cr-Commit-Position: %s\n' % _position
+
+  _git_svn_id = ('svn://svn.chromium.org/chrome/trunk/src@290386'
+                 ' 0039d316-1c4b-4281-b951-d872f2087c98')
+
+  _git_svn_id_footer = 'git-svn-id: %s\n' % _git_svn_id
+
+  _git_svn_id_branch = (
+      'svn://svn.chromium.org/chrome/branches/blabble/src@177288')
+
+  _git_svn_id_footer_branch = 'git-svn-id: %s\n' % _git_svn_id_branch
+
+
+  def testFootersBasic(self):
+    self.assertEqual(
+        git_footers.parse_footers(self._message), {})
+    self.assertEqual(
+        git_footers.parse_footers(self._message + self._position_footer),
+        { 'Cr-Commit-Position': [ self._position ] })
+    self.assertEqual(
+        git_footers.parse_footers(self._message + self._git_svn_id_footer),
+        { 'Git-Svn-Id': [ self._git_svn_id ] })
+    self.assertEqual(
+        git_footers.parse_footers(self._message + self._position_footer
+                                                + self._position_footer),
+        { 'Cr-Commit-Position': [ self._position, self._position ] })
+
+  def testTrunkHeuristic(self):
+    footers = git_footers.parse_footers(self._message + self._git_svn_id_footer)
+    self.assertEqual(
+        footers,
+        { 'Git-Svn-Id': [ self._git_svn_id ] })
+    self.assertEqual(
+        git_footers.get_position(footers),
+        ('refs/heads/master', '290386'))
+
+  def testBranchHeuristic(self):
+    footers = git_footers.parse_footers(self._message +
+                                        self._git_svn_id_footer_branch)
+    self.assertEqual(
+        footers,
+        { 'Git-Svn-Id': [ self._git_svn_id_branch ] })
+    self.assertEqual(
+        git_footers.get_position(footers),
+        ('refs/branch-heads/blabble', None))
+
+if __name__ == '__main__':
+  unittest.main()