feat(review): notify requester when review skipped for no new commits

[Koan-Bot]

What

When a /review finds no new commits since the last review, post a short blue > [!NOTE] comment instead of skipping silently.

Why

The incremental-review SHA check exists so unchanged PRs aren't re-reviewed. But on a user-initiated /review (or @mention), the bot only reacted with a thumbs-up and then went quiet — the requester couldn't tell whether the review ran, failed, or was intentionally skipped. They asked; they deserve an answer.

How

• New _post_no_changes_notice() in review_runner.py posts a build_alert("NOTE", …) blue callout (with the reviewed HEAD short-SHA) via the issues-comments API. Best-effort — a failed post only logs, so the skip still succeeds.
• Wired into the existing "same SHAs, not re-requested" skip branch, right before the success-with-skip return. Bot-comment triage on that path is unchanged.
• Spec updated contract-first (specs/skills/review.md → Outputs / side effects).

Testing

• New test asserts exactly one [!NOTE] skip notice is posted on the no-new-commits path; existing "skips silently" test still confirms the analysis is not run.
• make lint clean; full test_review_runner.py suite: 486 passed.

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Quality Report

Changes: 3 files changed, 74 insertions(+)

Code scan: 1 issue(s) found

• koan/app/review_runner.py:2200 — debug print statement

Tests: failed (4 failed, 403
tests)

Branch hygiene: clean

Generated by Skuggi

[Father-Koan]

PR Review — feat(review): notify requester when review skipped for no new commits

Small, well-scoped feature that closes a real UX gap — merge-ready with one non-blocking nit.

Strengths:

• Correct best-effort design: a failed notice POST only logs to stderr and returns False, so the skip still succeeds — the review is never held hostage to the comment call.
• Output is run through sanitize_github_comment(), and build_alert("NOTE", …) is the right primitive for a blue callout; no injection surface.
• Spec was updated contract-first, and the edit is purely additive (5 inserted bullets, no rewrites) — spec_change_guard.py passes it without an architectural declaration, so the discipline is satisfied.
• New test asserts observable behavior (exactly one [!NOTE] POST via run_gh call args), mocks the gh boundary correctly, and mirrors the existing passing skip test.

Notes on the automated quality report:

• "debug print statement at line 2200" is a false positive — that line is inside the _append_error_section_to_review docstring. The new print(..., file=sys.stderr) is legitimate best-effort logging, identical in style to _post_review_comment.

• "4 failed tests (403 collected)" could not be reproduced here (test execution needs approval unavailable in this read-only pass). It conflicts with the PR's own "486 passed" for test_review_runner.py, suggesting a different/partial collection or pre-existing flakiness. The two directly-affected tests are sound.

• Verify full CI is green before merge to reconcile the test-count discrepancy.

• Consider deduping/upserting the notice instead of a fresh POST (suggestion below) to match the rest of the module.

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🟢 Suggestions

1. No-changes notice is an un-deduped fresh POST — inconsistent with the module's upsert discipline
koan/app/review_runner.py:3335-3338

_post_no_changes_notice() always POSTs a brand-new issue comment. Every other comment this module leaves is deduped: the review summary is upserted (find_bot_comment + PATCH), and the bot-triage path uses fingerprinting. This one is not.

Why it matters: each time run_review hits the no-new-commits skip branch on an unchanged PR — repeated /review slash commands, or any future automated re-trigger with matching SHAs and no re-request — a fresh identical > [!NOTE] "No code changes" comment is appended. On a PR that gets poked more than once while stale, these accumulate as visible clutter. (An @mention is reaction-deduped upstream, so a single mention posts once; the risk is repeated explicit triggers.)

Suggested fix: before posting, look for a prior notice (a dedicated marker in the body via find_bot_comment) and upsert-or-skip, mirroring how the review summary is handled — so at most one live "skipped, unchanged" notice exists per PR. Non-blocking; the best-effort/error-swallowing behavior is otherwise correct.

_post_no_changes_notice(
    owner, repo, pr_number,
    head_sha=(current_shas[-1] if current_shas else ""),
)

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Checklist

• Durable-spec change declared or additive-only
• No injection in GitHub comment body (sanitized)
• Error paths handled (best-effort, no swallowed crash)
• Tests verify observable behavior, mock external boundaries
• Comment side effects deduped/upserted consistently — suggestion ＃1

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Automated review by Kōan (Claude) HEAD=a9f222e 5 min 56s

[Father-Koan]

Tip

No blocking issues found — ready to merge.