Allow commenting on files from earlier commits of a pull request

[artur-czuba-iyuno]

Refs #4315, #2793

Files opened from the Commits node get a review URI carrying the sha of that commit. findMatchedFileChangeForReviewDiffView only ever compares that sha against the pull request head and the merge base, so any other commit fails to match, no commenting ranges are produced, and the gutter stays empty. This is why commenting has always happened to work on the newest commit and nowhere else, as observed in #2793.

Comments are created through addPullRequestReviewThread, which takes only path, line and side — no commit id — so a new thread is always anchored to the head of the pull request. Simply relaxing the sha comparison would place comments at the same line number in the head diff, which is silently wrong for any file that changed after the commit being viewed.

This change therefore allows commenting on a commit's file only when the file is unchanged between that commit and the head. In that case the document's line numbers are by definition the head's line numbers, so no position translation is needed and the comment lands exactly where it was written — matching what the GitHub web UI does when reviewing changes.

• provideCommitCommentingRanges provides ranges from diffBetween(base.sha, commit, file), so every offered line is part of the pull request diff and is accepted by the mutation.
• When the file has changed since the commit, commenting is disabled and the file gets a warning icon in the Commits tree. Hovering explains why, names the most recent commit that touched the file, and offers a link to open the version of the file that can be commented on. The git lookup happens in resolveTreeItem, so it only runs for the file actually hovered; detecting which files changed costs one diffBetween per commit node, not one per file.
• The thread reconciliation in _pendingCommentThreadAdds is made URI-aware. Without it the newly created thread fails to match the incoming one and gets duplicated.

Testing

New tests in src/test/view/reviewCommentController.test.ts cover the three cases: ranges are provided for a file that has not changed since the commit, commenting is disabled for a file that has changed, and a document of the head commit is left to the existing code path.

Verified manually against a checked out pull request, including the warning icon, its hover, and the link to the latest version of the file.

Not covered here

Anchoring a thread to a specific commit via the REST API (commit_id), which would also enable commenting on files that changed later and let GitHub mark such threads as outdated. That is the larger part of #4315 and would add a second code path for creating comments next to the GraphQL one. Happy to follow up with it if that is the direction you would prefer.

Added files under a commit need #8866 as well, otherwise the head side of their diff is the base document and this code path does not apply to them. The two changes are independent.

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[Copilot]

Pull request overview

Enables inline commenting when viewing a file from an earlier PR commit in the Commits tree, but only when that file is unchanged between the viewed commit and the PR head (so comment line numbers remain unambiguous and land correctly on the head).

Changes:

• Add a commit-aware commenting-ranges path in ReviewCommentController that uses diffBetween(base.sha, commit, file) and disables commenting when the file changed after the viewed commit.
• Mark files in the Commits tree that changed after the viewed commit with a warning icon and a tooltip that explains why commenting is disabled and links to the latest commentable version.
• Make pending-thread reconciliation and thread creation logic URI-aware so newly created threads match incoming threads and don’t duplicate.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/view/treeNodes/fileChangeNode.ts	Adds “changed since commit” warning state, tooltip building, and link to open the latest file version.
src/view/treeNodes/commitNode.ts	Computes which files changed between a commit and PR head, and marks affected file nodes.
src/view/reviewCommentController.ts	Adds commit-document detection and commit-scoped commenting-range computation with “unchanged since commit” gating.
src/test/view/reviewCommentController.test.ts	Adds tests covering commit-document commenting ranges enabled/disabled behavior and head-commit fallback.
src/commands.ts	Registers a command used by the tooltip link to open the latest version of a file in the PR changes list.

Comments suppressed due to low confidence (1)

src/view/treeNodes/fileChangeNode.ts:380

• The commit message is appended via appendMarkdown, so a crafted commit subject (e.g. containing markdown links) can inject additional links into the tooltip. Even with a restricted isTrusted, using appendText here prevents markdown injection and avoids surprising rendering.

				if (log.length) {
					const message = log[0].message.split('\n')[0];
					tooltip.appendMarkdown('\n\n' + vscode.l10n.t('Last changed in {0}: {1}', log[0].hash.substring(0, 8), message));
				}

[Angie20182]

Request Id: 39e943e2-aed1-44e2-a137-a3e4b7000200
Correlation Id: e94a2ca2-30b0-1000-a157-f18c22c7e480
Timestamp: 2026-07-30T10:11:44Z
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