81 lines
4.5 KiB
TypeScript
81 lines
4.5 KiB
TypeScript
import {join} from 'path';
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import {PullRequestFailure} from '../failures';
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import {PullRequest} from '../pull-request';
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import {MergeStrategy, TEMP_PR_HEAD_BRANCH} from './strategy';
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/** Path to the commit message filter script. Git expects this paths to use forward slashes. */
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const MSG_FILTER_SCRIPT = join(__dirname, './commit-message-filter.js').replace(/\\/g, '/');
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/**
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* Merge strategy that does not use the Github API for merging. Instead, it fetches
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* all target branches and the PR locally. The PR is then cherry-picked with autosquash
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* enabled into the target branches. The benefit is the support for fixup and squash commits.
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* A notable downside though is that Github does not show the PR as `Merged` due to non
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* fast-forward merges
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*/
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export class AutosquashMergeStrategy extends MergeStrategy {
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/**
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* Merges the specified pull request into the target branches and pushes the target
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* branches upstream. This method requires the temporary target branches to be fetched
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* already as we don't want to fetch the target branches per pull request merge. This
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* would causes unnecessary multiple fetch requests when multiple PRs are merged.
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* @throws {GitCommandError} An unknown Git command error occurred that is not
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* specific to the pull request merge.
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* @returns A pull request failure or null in case of success.
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*/
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async merge(pullRequest: PullRequest): Promise<PullRequestFailure|null> {
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const {prNumber, targetBranches, requiredBaseSha, needsCommitMessageFixup} = pullRequest;
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// In case a required base is specified for this pull request, check if the pull
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// request contains the given commit. If not, return a pull request failure. This
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// check is useful for enforcing that PRs are rebased on top of a given commit. e.g.
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// a commit that changes the codeowner ship validation. PRs which are not rebased
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// could bypass new codeowner ship rules.
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if (requiredBaseSha && !this.git.hasCommit(TEMP_PR_HEAD_BRANCH, requiredBaseSha)) {
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return PullRequestFailure.unsatisfiedBaseSha();
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}
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// SHA for the first commit the pull request is based on. Usually we would able
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// to just rely on the base revision provided by `getPullRequestBaseRevision`, but
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// the revision would rely on the amount of commits in a pull request. This is not
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// reliable as we rebase the PR with autosquash where the amount of commits could
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// change. We work around this by parsing the base revision so that we have a fixated
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// SHA before the autosquash rebase is performed.
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const baseSha =
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this.git.run(['rev-parse', this.getPullRequestBaseRevision(pullRequest)]).stdout.trim();
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// Git revision range that matches the pull request commits.
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const revisionRange = `${baseSha}..${TEMP_PR_HEAD_BRANCH}`;
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// We always rebase the pull request so that fixup or squash commits are automatically
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// collapsed. Git's autosquash functionality does only work in interactive rebases, so
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// our rebase is always interactive. In reality though, unless a commit message fixup
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// is desired, we set the `GIT_SEQUENCE_EDITOR` environment variable to `true` so that
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// the rebase seems interactive to Git, while it's not interactive to the user.
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// See: https://github.com/git/git/commit/891d4a0313edc03f7e2ecb96edec5d30dc182294.
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const branchBeforeRebase = this.git.getCurrentBranch();
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const rebaseEnv =
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needsCommitMessageFixup ? undefined : {...process.env, GIT_SEQUENCE_EDITOR: 'true'};
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this.git.run(
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['rebase', '--interactive', '--autosquash', baseSha, TEMP_PR_HEAD_BRANCH],
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{stdio: 'inherit', env: rebaseEnv});
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// Update pull requests commits to reference the pull request. This matches what
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// Github does when pull requests are merged through the Web UI. The motivation is
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// that it should be easy to determine which pull request contained a given commit.
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// **Note**: The filter-branch command relies on the working tree, so we want to make
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// sure that we are on the initial branch where the merge script has been run.
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this.git.run(['checkout', '-f', branchBeforeRebase]);
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this.git.run(
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['filter-branch', '-f', '--msg-filter', `${MSG_FILTER_SCRIPT} ${prNumber}`, revisionRange]);
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// Cherry-pick the pull request into all determined target branches.
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const failedBranches = this.cherryPickIntoTargetBranches(revisionRange, targetBranches);
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if (failedBranches.length) {
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return PullRequestFailure.mergeConflicts(failedBranches);
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}
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this.pushTargetBranchesUpstream(targetBranches);
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return null;
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}
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}
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