Add `pr-base-commit` feature (#6538)

Co-authored-by: Yakov <16872793+yakov116@users.noreply.github.com>

1 files changed, 85 insertions, 0 deletions

diff --git a/source/features/pr-base-commit.tsx b/source/features/pr-base-commit.tsx
new file mode 100644
index 00000000..42d3e3a6
--- /dev/null
+++ b/source/features/pr-base-commit.tsx
@@ -0,0 +1,85 @@
+import React from 'dom-chef';
+import select from 'select-dom';
+
+import * as pageDetect from 'github-url-detection';
+
+import features from '../feature-manager';
+import observe from '../helpers/selector-observer';
+import * as api from '../github-helpers/api';
+import {getBranches} from '../github-helpers/pr-branches';
+import getPrInfo, {PullRequestInfo} from '../github-helpers/get-pr-info';
+import pluralize from '../helpers/pluralize';
+import {buildRepoURL} from '../github-helpers';
+import {linkifyCommit} from '../github-helpers/dom-formatters';
+import {removeTextNodeContaining} from '../helpers/dom-utils';
+
+function getBaseCommitNotice(prInfo: PullRequestInfo): JSX.Element {
+	const {base} = getBranches();
+	const commit = linkifyCommit(prInfo.baseRefOid);
+	const count = pluralize(prInfo.behindBy, '$$ commit');
+	const countLink = (
+		<a href={buildRepoURL('compare', `${prInfo.baseRefOid.slice(0, 8)}...${base.branch}`)}>
+			{count}
+		</a>
+	);
+	return (
+		<>It’s {countLink} behind (base commit: {commit})</>
+	);
+}
+
+async function addInfo(statusMeta: Element): Promise<void> {
+	// Selector copied from GitHub. Don't @ me
+	// This excludes hidden ".status-meta" items without adding this longass selector to the observer
+	// Added: .rgh-update-pr-from-base-branch-row
+	if (!statusMeta.closest('.merge-pr.is-merging .merging-body, .merge-pr.is-merging .merge-commit-author-email-info, .merge-pr.is-merging-solo .merging-body, .merge-pr.is-merging-jump .merging-body, .merge-pr.is-merging-group .merging-body, .merge-pr.is-rebasing .rebasing-body, .merge-pr.is-squashing .squashing-body, .merge-pr.is-squashing .squash-commit-author-email-info, .merge-pr.is-merging .branch-action-state-error-if-merging .merging-body-merge-warning, .rgh-update-pr-from-base-branch-row')) {
+		return;
+	}
+
+	const {base} = getBranches();
+	const prInfo = await getPrInfo(base.relative);
+	if (!prInfo.needsUpdate) {
+		return;
+	}
+
+	const previousMessage = statusMeta.firstChild!; // Extract now because it won't be the first child anymore
+	statusMeta.prepend(getBaseCommitNotice(prInfo));
+	removeTextNodeContaining(previousMessage, 'Merging can be performed automatically.');
+}
+
+async function init(signal: AbortSignal): Promise<false | void> {
+	await api.expectToken();
+
+	observe('.branch-action-item .status-meta', addInfo, {signal});
+}
+
+void features.add(import.meta.url, {
+	include: [
+		pageDetect.isPRConversation,
+	],
+	exclude: [
+		pageDetect.isClosedPR,
+		() => select('.head-ref')!.title === 'This repository has been deleted',
+	],
+	awaitDomReady: true, // DOM-based exclusions
+	init,
+});
+
+/*
+Test URLs
+
+PR without conflicts
+https://github.com/refined-github/sandbox/pull/60
+
+Draft PR without conflicts
+https://github.com/refined-github/sandbox/pull/61
+
+Native "Update branch" button
+(pick a conflict-free PR from https://github.com/refined-github/refined-github/pulls?q=is%3Apr+is%3Aopen+sort%3Acreated-asc)
+
+Native "Resolve conflicts" button
+https://github.com/refined-github/sandbox/pull/9
+
+Cross-repo PR with long branch names
+https://github.com/refined-github/sandbox/pull/13
+
+*/