Link commit SHAs in inline file comments (#8278)

* Initial plan

* Initial analysis complete

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

* Add commit SHA linking to file view comments

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

* Add tests for commit SHA regex pattern

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

* Extract COMMIT_SHA_EXPRESSION as exported constant

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

* Revert unrelated type definition change

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

* Fix test: regex correctly excludes SHAs in backticks

Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: alexr00 <38270282+alexr00@users.noreply.github.com>

Author: Copilot

src/github/prComment.ts

@@ -217,6 +217,7 @@ export class TemporaryComment extends CommentBase {
 const SUGGESTION_EXPRESSION = /```suggestion(\u0020*(\r\n|\n))((?<suggestion>[\s\S]*?)(\r\n|\n))?```/;
 const IMG_EXPRESSION = /<img .*src=['"](?<src>.+?)['"].*?>/g;
 const UUID_EXPRESSION = /[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-5][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}/;
+export const COMMIT_SHA_EXPRESSION = /(?<![`\/\w])([0-9a-f]{7})([0-9a-f]{33})?(?![`\/\w])/g;
 
 export class GHPRComment extends CommentBase {
 	private static ID = 'GHPRComment';
@@ -421,6 +422,36 @@ ${lineContents}
 		return replaceImages(body, html, this.githubRepository?.remote.host);
 	}
 
+	private replaceCommitShas(body: string): string {
+		const githubRepository = this.githubRepository;
+		if (!githubRepository) {
+			return body;
+		}
+
+		// Match commit SHAs that are:
+		// - Either 7 or 40 hex characters
+		// - Not already part of a URL or markdown link
+		// - Not inside code blocks (backticks)
+		return body.replace(COMMIT_SHA_EXPRESSION, (match, shortSha, remaining, offset) => {
+			// Don't replace if inside code blocks
+			const beforeMatch = body.substring(0, offset);
+			const backtickCount = (beforeMatch.match(/`/g)?.length ?? 0);
+			if (backtickCount % 2 === 1) {
+				return match;
+			}
+
+			// Don't replace if already part of a markdown link
+			if (beforeMatch.endsWith('[') || body.substring(offset + match.length).startsWith(']')) {
+				return match;
+			}
+
+			const owner = githubRepository.remote.owner;
+			const repo = githubRepository.remote.repositoryName;
+			const commitUrl = `https://${githubRepository.remote.host}/${owner}/${repo}/commit/${match}`;
+			return `[${shortSha}](${commitUrl})`;
+		});
+	}
+
 	private replaceNewlines(body: string) {
 		return body.replace(/(?<!\s)(\r\n|\n)/g, '  \n');
 	}
@@ -463,7 +494,8 @@ ${lineContents}
 			return `${substring.startsWith('@') ? '' : substring.charAt(0)}[@${username}](${url})`;
 		});
 
-		const permalinkReplaced = await this.replacePermalink(linkified);
+		const commitShasReplaced = this.replaceCommitShas(linkified);
+		const permalinkReplaced = await this.replacePermalink(commitShasReplaced);
 		await emojiPromise;
 		return this.postpendSpecialAuthorComment(emojify(this.replaceImg(this.replaceSuggestion(permalinkReplaced))));
 	}

src/test/github/prComment.test.ts

@@ -4,7 +4,56 @@
  *--------------------------------------------------------------------------------------------*/
 
 import { default as assert } from 'assert';
-import { replaceImages } from '../../github/prComment';
+import { COMMIT_SHA_EXPRESSION, replaceImages } from '../../github/prComment';
+
+describe('commit SHA replacement', function () {
+	it('should match 7-character commit SHAs', function () {
+		const text = 'Fixed in commit 5cf56bc and also in abc1234';
+		const matches = Array.from(text.matchAll(COMMIT_SHA_EXPRESSION));
+		assert.strictEqual(matches.length, 2);
+		assert.strictEqual(matches[0][1], '5cf56bc');
+		assert.strictEqual(matches[1][1], 'abc1234');
+	});
+
+	it('should match 40-character commit SHAs', function () {
+		const text = 'Fixed in commit 5cf56bc1234567890abcdef1234567890abcdef0';
+		const matches = Array.from(text.matchAll(COMMIT_SHA_EXPRESSION));
+		assert.strictEqual(matches.length, 1);
+		assert.strictEqual(matches[0][0], '5cf56bc1234567890abcdef1234567890abcdef0');
+	});
+
+	it('should not match SHAs in URLs', function () {
+		const text = 'https://github.com/owner/repo/commit/5cf56bc';
+		const matches = Array.from(text.matchAll(COMMIT_SHA_EXPRESSION));
+		assert.strictEqual(matches.length, 0);
+	});
+
+	it('should not match SHAs in code blocks', function () {
+		const text = 'Fixed in commit 5cf56bc but not in `abc1234`';
+		const matches = Array.from(text.matchAll(COMMIT_SHA_EXPRESSION));
+		// The regex should only match the first SHA, not the one inside backticks
+		assert.strictEqual(matches.length, 1);
+		assert.strictEqual(matches[0][1], '5cf56bc');
+	});
+
+	it('should not match non-hex strings', function () {
+		const text = 'Not a SHA: 1234xyz or ABCDEFG';
+		const matches = Array.from(text.matchAll(COMMIT_SHA_EXPRESSION));
+		assert.strictEqual(matches.length, 0);
+	});
+
+	it('should not match SHAs with alphanumeric prefix', function () {
+		const text = 'prefix5cf56bc is not a SHA';
+		const matches = Array.from(text.matchAll(COMMIT_SHA_EXPRESSION));
+		assert.strictEqual(matches.length, 0);
+	});
+
+	it('should not match SHAs with alphanumeric suffix', function () {
+		const text = '5cf56bcsuffix is not a SHA';
+		const matches = Array.from(text.matchAll(COMMIT_SHA_EXPRESSION));
+		assert.strictEqual(matches.length, 0);
+	});
+});
 
 describe('replace images', function () {
 	it('github.com', function () {