flutter/dev/tools/bin/find_commit.dart
Nate Bosch fa3a37c76d
Use merge-base in find_commit.dart (#138033)
Closes #97595

The prior approach of manually diffing the entire log chain is less
efficient, and only found the original branch point ignoring subsequent
merges. The limitation forced PR workflows into rebasing and force
pushing new history to get the branch point far enough for CI to pass.

Use `git merge-base` to find the latest common commit with the main
branch.
Add an `allowFailure` argument to the `git` utility to use a more
specific failure in the case of no shared history when this command will
fail with a generic error.

Use `^branch` with the `git log` commands to exclude shared history and
more easily count the unique commits on each branch.

Drop the `Commit` abstraction. Parse directly to timestamp or line counts.
2023-11-10 02:15:27 +00:00

92 lines
3.9 KiB
Dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// This script looks at the current commit and branch of the git repository in
// which it was run, and finds the contemporary commit in the master branch of
// another git repository, whose path is provided on the command line. The
// contemporary commit is the one that was public at the time of the last commit
// on the master branch before the current commit's branch was created.
import 'dart:io';
const bool debugLogging = false;
void log(String message) {
if (debugLogging) {
print(message);
}
}
const String _commitTimestampFormat = '--format=%cI';
DateTime _parseTimestamp(String line) => DateTime.parse(line.trim());
int _countLines(String output) => output.trim().split('/n').where((String line) => line.isNotEmpty).length;
String findCommit({
required String primaryRepoDirectory,
required String primaryBranch,
required String primaryTrunk,
required String secondaryRepoDirectory,
required String secondaryBranch,
}) {
final DateTime anchor;
if (primaryBranch == primaryTrunk) {
log('on $primaryTrunk, using last commit time');
anchor = _parseTimestamp(git(primaryRepoDirectory, <String>['log', _commitTimestampFormat, '--max-count=1', primaryBranch, '--']));
} else {
final String mergeBase = git(primaryRepoDirectory, <String>['merge-base', primaryBranch, primaryTrunk], allowFailure: true).trim();
if (mergeBase.isEmpty) {
throw StateError('Branch $primaryBranch does not seem to have a common history with trunk $primaryTrunk.');
}
anchor = _parseTimestamp(git(primaryRepoDirectory, <String>['log', _commitTimestampFormat, '--max-count=1', mergeBase, '--']));
if (debugLogging) {
final int missingTrunkCommits = _countLines(git(primaryRepoDirectory, <String>['rev-list', primaryTrunk, '^$primaryBranch', '--']));
final int extraCommits = _countLines(git(primaryRepoDirectory, <String>['rev-list', primaryBranch, '^$primaryTrunk', '--']));
if (missingTrunkCommits == 0 && extraCommits == 0) {
log('$primaryBranch is even with $primaryTrunk at $mergeBase');
} else {
log('$primaryBranch branched from $primaryTrunk $missingTrunkCommits commits ago, trunk has advanced by $extraCommits commits since then.');
}
}
}
return git(secondaryRepoDirectory, <String>[
'log',
'--format=%H',
'--until=${anchor.toIso8601String()}',
'--max-count=1',
secondaryBranch,
'--',
]);
}
String git(String workingDirectory, List<String> arguments, {bool allowFailure = false}) {
final ProcessResult result = Process.runSync('git', arguments, workingDirectory: workingDirectory);
if (!allowFailure && result.exitCode != 0 || '${result.stderr}'.isNotEmpty) {
throw ProcessException('git', arguments, '${result.stdout}${result.stderr}', result.exitCode);
}
return '${result.stdout}';
}
void main(List<String> arguments) {
if (arguments.isEmpty || arguments.length > 2 || arguments.contains('--help') || arguments.contains('-h')) {
print(
'Usage: dart find_commit.dart [<path-to-primary-repo>] <path-to-secondary-repo>\n'
'This script will find the commit in the secondary repo that was contemporary\n'
'when the commit in the primary repo was created. If that commit is on a\n'
"branch, then the date of the branch's last merge is used instead.\n"
'If <path-to-primary-repo> is omitted, the current directory is used for the\n'
'primary repo.'
);
} else {
final String primaryRepo = arguments.length == 1 ? '.' : arguments.first;
final String secondaryRepo = arguments.last;
print(findCommit(
primaryRepoDirectory: primaryRepo,
primaryBranch: git(primaryRepo, <String>['rev-parse', '--abbrev-ref', 'HEAD']).trim(),
primaryTrunk: 'master',
secondaryRepoDirectory: secondaryRepo,
secondaryBranch: 'master',
).trim());
}
}