Add update.py to easily update the imported in-tree copy of Crashpad

third_party/crashpad/update.py

Index: third_party/crashpad/update.py
diff --git a/third_party/crashpad/update.py b/third_party/crashpad/update.py
new file mode 100755
index 0000000000000000000000000000000000000000..97d3bd576087382b286f08d7ce94d2158d53ce77
--- /dev/null
+++ b/third_party/crashpad/update.py
@@ -0,0 +1,218 @@
+#!/usr/bin/env python
+# coding: utf-8
+
+# Copyright 2015 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 os
+import re
+import subprocess
+import sys
+import textwrap
+
+
+def SubprocessCheckCall0Or1(args):
+    """Like subprocss.check_call(), but allows a return code of 1.
+
+    Returns True if the subprocess exits with code 0, False if it exits with
+    code 1, and re-raises the subprocess.check_call() exception otherwise.
+    """
+    try:
+        subprocess.check_call(args)
+    except subprocess.CalledProcessError, e:
+        if e.returncode != 1:
+            raise
+        return False
+
+    return True
+
+
+def GitMergeBaseIsAncestor(ancestor, descendant):
+    """Determines whether |ancestor| is an ancestor of |descendant|.
+    """
+    return SubprocessCheckCall0Or1(
+        ['git', 'merge-base', '--is-ancestor', ancestor, descendant])
+
+
+def main(args):
+    parser = argparse.ArgumentParser(
+        description='Update the in-tree copy of an imported project')
+    parser.add_argument(
+        '--repository',
+        default='https://chromium.googlesource.com/crashpad/crashpad',
+        help='The imported project\'s remote fetch URL',
+        metavar='URL')
+    parser.add_argument(
+        '--subtree',
+        default='third_party/crashpad/crashpad',
+        help='The imported project\'s location in this project\'s tree',
+        metavar='PATH')
+    parser.add_argument(
+        '--update-to',
+        default='FETCH_HEAD',
+        help='What to update the imported project to',
+        metavar='COMMITISH')
+    parser.add_argument(
+        '--fetch-ref',
+        default='HEAD',
+        help='The remote ref to fetch',
+        metavar='REF')
+    parser.add_argument(
+        '--readme',
+        help='The README.chromium file describing the imported project',
+        metavar='FILE',
+        dest='readme_path')
+    parsed = parser.parse_args(args)
+
+    original_head = (
+        subprocess.check_output(['git', 'rev-parse', 'HEAD']).rstrip())
+
+    # Read the README, because that’s what it’s for. Extract some things from
+    # it, and save it to be able to update it later.
+    readme_path = (parsed.readme_path or
+                   os.path.join(os.path.dirname(__file__ or '.'),
+                                'README.chromium'))
+    readme_content_old = open(readme_path).read()
+
+    project_name_match = re.search(
+        r'^Name:\s+(.*)$', readme_content_old, re.MULTILINE)
+    project_name = project_name_match.group(1)
+
+    # Extract the original commit hash from the README.
+    revision_match = re.search(r'^Revision:\s+([0-9a-fA-F]{40})($|\s)',
+                               readme_content_old,
+                               re.MULTILINE)
+    revision_old = revision_match.group(1)
+
+    subprocess.check_call(['git', 'fetch', parsed.repository, parsed.fetch_ref])
+
+    # Make sure that parsed.update_to is an ancestor of FETCH_HEAD, and
+    # revision_old is an ancestor of parsed.update_to. This prevents the use of
+    # hashes that are known to git but that don’t make sense in the context of
+    # the update operation.
+    if not GitMergeBaseIsAncestor(parsed.update_to, 'FETCH_HEAD'):
+        raise Exception('update_to is not an ancestor of FETCH_HEAD',
+                        parsed.update_to,
+                        'FETCH_HEAD')
+    if not GitMergeBaseIsAncestor(revision_old, parsed.update_to):
+        raise Exception('revision_old is not an ancestor of update_to',
+                        revision_old,
+                        parsed.update_to)
+
+    update_range = revision_old + '..' + parsed.update_to
+
+    # This cherry-picks each change in the window from the upstream project into
+    # the current branch.
+    assisted_cherry_pick = False
+    try:
+        if not SubprocessCheckCall0Or1(['git',
+                                        'cherry-pick',
+                                        '--keep-redundant-commits',
+                                        '--strategy=subtree',
+                                        '-Xsubtree=' + parsed.subtree,
+                                        '-x',
+                                        update_range]):
+            assisted_cherry_pick = True
+            print >>sys.stderr, ("""
+Please fix the errors above and run "git cherry-pick --continue".
+Press Enter when "git cherry-pick" completes.
+You may use a new shell for this, or ^Z if job control is available.
+Press ^C to abort.
+""")
+            raw_input()
+    except:
+        # ^C, signal, or something else.
+        print >>sys.stderr, 'Aborting...'
+        subprocess.call(['git', 'cherry-pick', '--abort'])
+        raise
+
+    # Get an abbreviated hash and subject line for each commit in the window,
+    # sorted in chronological order.
+    log_lines = subprocess.check_output(['git',
+                                         '-c',
+                                         'core.abbrev=12',
+                                         'log',
+                                         '--abbrev-commit',
+                                         '--pretty=oneline',
+                                         '--reverse',
+                                         update_range]).splitlines(False)
+
+    if assisted_cherry_pick:
+        # If the user had to help, count the number of cherry-picked commits,
+        # expecting it to match.
+        cherry_picked_commits = int(subprocess.check_output(
+            ['git', 'rev-list', '--count', original_head + '..HEAD']))
+        if cherry_picked_commits != len(log_lines):
+            print >>sys.stderr, 'Something smells fishy, aborting anyway...'
+            subprocess.call(['git', 'cherry-pick', '--abort'])
+            raise Exception('not all commits were cherry-picked',
+                            len(log_lines),
+                            cherry_picked_commits)
+
+    # Make a nice commit message. Start with the full commit hash.
+    revision_new = subprocess.check_output(
+        ['git', 'rev-parse', parsed.update_to]).rstrip()
+    new_message = 'Update ' + project_name + ' to ' + revision_new + '\n\n'
+
+    # Wrap everything to 72 characters, with a hanging indent.
+    wrapper = textwrap.TextWrapper(width=72, subsequent_indent = ' ' * 13)
+    for line in log_lines:
+        # Strip trailing periods from subjects.
+        if line.endswith('.'):
+            line = line[:-1]
+
+        # If any subjects have what look like commit hashes in them, truncate
+        # them to 12 characters.
+        line = re.sub(r'(\s)([0-9a-fA-F]{12})([0-9a-fA-F]{28})($|\s)',
+                      r'\1\2\4',
+                      line)
+
+        new_message += '\n'.join(wrapper.wrap(line)) + '\n'
+
+    # Update the README with the new hash.
+    readme_content_new = re.sub(
+        r'^(Revision:\s+)([0-9a-fA-F]{40})($|\s.*?$)',
+        r'\g<1>' + revision_new,
+        readme_content_old,
+        1,
+        re.MULTILINE)
+
+    # If the in-tree copy has no changes relative to the upstream, clear the
+    # “Local Modifications” section of the README.
+    has_local_modifications = True
+    if SubprocessCheckCall0Or1(['git',
+                                'diff-tree',
+                                '--quiet',
+                                parsed.update_to,
+                                'HEAD:' + parsed.subtree]):
+        has_local_modifications = False
+
+        readme_content_new = re.sub(r'\nLocal Modifications:\n.*$',
+                                    '\nLocal Modifications:\nNone.',
+                                    readme_content_new,
+                                    1)
+
+    # This soft-reset causes all of the cherry-picks to show up as staged,
+    # which will have the effect of squashing them along with the README update
+    # when committed below.
+    subprocess.check_call(['git', 'reset', '--soft', original_head])
+
+    # Write the new README.
+    open(readme_path, 'w').write(readme_content_new)
+
+    # Commit everything.
+    subprocess.check_call(['git', 'add', readme_path])
+    subprocess.check_call(['git', 'commit', '--message=' + new_message])
+
+    if has_local_modifications:
+        print >>sys.stderr, (
+            'Remember to check the Local Modifications section in ' +
+            readme_path)
+
+    return 0
+
+
+if __name__ == '__main__':
+    sys.exit(main(sys.argv[1:]))