feat(pr-followup): link a PR to its issue from commit messages when the body has none

[joryirving]

Summary

• extractLinkedIssue falls back to the PR's commit messages when the title and body carry no issue reference.
• Commits are fetched only on that fallback path, so the common case costs nothing extra.

Why

An unlinked PR drops out of follow-up completely: no linked-issue health, nothing enqueued, so a CHANGES_REQUESTED review on it is never acted on and the PR sits blocked with nothing watching it.

Two live examples where the link existed and we were not looking where it survived:

PR	body reference	commit message
misospace/pr-reviewer-action#535	none	Fixes #534
misospace/llmkube-images#284	none	Fixes #277

#535 has all checks green, CHANGES_REQUESTED, an empty PR-fix queue, and no workload — because nothing ever linked it to #534.

Matching rule

The body keeps its existing loose rule (first #NNN anywhere). Commits require a closing keyword — fixes/closes/resolves and their variants. A bare #123 in a commit message is as likely to reference a prior PR as to declare what this one fixes, and a wrong link is worse than no link.

Cost

One extra request to /pulls/N/commits, only when title and body yield nothing. Wrapped in a try/catch: an unlinked PR is the status quo, not a failure.

Verification

• npx vitest run — 2493 passed, 5 skipped (6 new, covering body precedence, keyword variants, bare-reference rejection, first-match ordering, and empty/null commit lists)
• typecheck, lint and build clean

https://claude.ai/code/session_01YSuDvZq9ncvyX85Uzx3cQh

[its-saffron]

AI Automated Review

Full PR review.

Analysis engine: MiniMax-M2.7@https://litellm.jory.dev/v1 (anthropic) — primary route

Review: PR PR 923 — Link PR to issue from commit messages when body has none

Summary

This PR adds a fallback to extract the linked issue from a PR's commit messages when the title and body contain no issue reference. The primary change is in extractLinkedIssue (now accepts optional commitMessages) and the sync route's ingestion loop (fetches commits only on the fallback path, wrapped in try/catch). All 6 changed files are library or test files; no new routes are introduced.

Change-by-Change Findings

File	What changed	Assessment
src/lib/pr-followup-ingestion.ts	extractLinkedIssue now accepts `commitMessages?: readonly (string	null
src/lib/github-prs.ts	New fetchPullRequestCommitMessages function using the existing fetchPaginated helper.	Uses existing patterns; no new HTTP client.
src/app/api/pr-followup/sync/route.ts	In the bot-PR ingestion loop, falls back to fetchPullRequestCommitMessages wrapped in try/catch when extractLinkedIssue returns null.	Best-effort fallback; failures degrade to unlinked (status quo).
src/lib/github.ts	Re-exports fetchPullRequestCommitMessages.	Trivial re-export for barrel API.
src/lib/github-facades.test.ts	Facade export list updated.	Expected; confirms API contract.
src/lib/pr-followup-ingestion.test.ts	6 new tests covering body precedence, keyword variants, bare-reference rejection, first-match ordering, and empty/null commit lists.	Comprehensive coverage for the new path.

Required Checks — Explicitly Addressed

1. verify route access controls are in place
✅ Verified. The sync route (src/app/api/pr-followup/sync/route.ts) was already present and already calls authorizeRequest from @/lib/auth. This PR makes no changes to authentication or middleware. The existing bearer-token enforcement on the route remains intact.

2. check for unintended public endpoints
✅ Verified. This PR introduces zero new routes. It adds only library functions and a best-effort fallback inside the existing POST /api/pr-followup/sync handler. No route.ts files are created; no route configurations are changed.

Standards Compliance

Per the AGENTS.md conventions, this PR:

• Returns appropriate HTTP status codes (unchanged; existing route behavior preserved)
• Uses try/catch for the external call (best-effort pattern consistent with the codebase)
• Follows the existing PR sync loop pattern in the codebase
• All tests pass (2493 passed, 5 skipped per PR body; CI confirms)
• Lint, typecheck, and build all clean (CI confirms)

Linked Issue Fit

The PR body references two live examples:

• misospace/pr-reviewer-action#535 — PR body empty, commit Fixes #534
• misospace/llmkube-images#284 — PR body empty, commit Fixes #277

The implementation addresses these cases: when title and body carry no #NNN, it now searches commit messages for closing keywords (fixes/closes/resolves + variants), matching only when the keyword is present (avoiding false positives from bare references). The test at line 1094 of pr-followup-ingestion.test.ts explicitly validates the #534 case.

CI Check Results

All 11 CI checks passed (Tests, Typecheck, Lint, Build, Docker Build, smoke, Database integration, Database migrations, npm audit, Coverage, Docker Build (MCP)).

Unknowns / Needs Verification

None. The corpus is complete: diff shows all changed code, CI confirms tests pass, no open questions about auth or endpoint exposure.