# Problem 018: .husky/pre-commit auto-write hook's `--diff-filter=ACM` excludes R (renamed)

**Status**: Closed
**Reported**: 2026-05-30
**Priority**: 6 (Medium) — Impact: Minor (2) x Likelihood: Possible (3)
**Origin**: internal
**Effort**: S — one-character diff-filter change (ACM → ACMR) in `.husky/pre-commit` + REQ-PRECOMMIT-AUTO-WRITE-RESTAGE rename-with-edit test
**WSJF**: 6.0 = (6 × 1.0) / 1
**Type**: technical

## Description

`.husky/pre-commit` auto-write hook's `--diff-filter=ACM` excludes R (renamed) — rename-with-edit commits bypass auto-write and `format:check` rejects.

Local fix path (.husky/pre-commit + ADR-0016 confirmation note + REQ-PRECOMMIT-AUTO-WRITE-RESTAGE test fixture).

Evidence: this session's commit `c0dfae8` (run-retro session-wrap closing P009 + briefing refresh) was REJECTED on first try by `format:check` after the auto-write step skipped the renamed `docs/problems/closed/009-...md` (renamed-with-edit from `verifying/009-...md` + Edit-tool Status field update + `## Verification observed` section append). Recovered with manual `npm run format && git add ...`. The hook's `git diff --cached --name-only --diff-filter=ACM` only catches A/C/M; R is excluded. P009's verification contract held for plain Modify but not for rename-with-edit — a related-but-distinct gap.

Fix shape: change diff-filter to `ACMR` so renames pass through. Also extend the REQ-PRECOMMIT-AUTO-WRITE-RESTAGE test to assert the rename-with-edit case.

## Symptoms

- A rename-with-edit staged commit (e.g. `git mv old new` + Edit-tool change to the renamed file) bypasses the auto-write block.
- `format:check` rejects the commit on first try because the renamed file is unformatted.
- The hook's auto-write log lists only A/C/M files; the renamed file is absent.
- Recovery requires manual `npm run format && git add <renamed>` then re-commit.

## Workaround

Manually run `npm run format && git add <renamed-file>` after the format:check rejection, then retry the commit. The auto-write skip is silent — the user must notice the renamed file is missing from the auto-write log to know what to re-stage.

## Impact Assessment

- **Who is affected**: this project's maintainer (rename-with-edit commits are common in ITIL ticket transitions: `git mv open/NNN-*.md known-error/NNN-*.md` + Edit-tool Status field update).
- **Frequency**: every rename-with-edit commit (P016 verifying transition exercised this earlier the same day; P009 closure cited it explicitly).
- **Severity**: Medium — non-fatal but reintroduces exactly the friction P009 was meant to eliminate, for the rename shape.
- **Analytics**: N/A (local dev workflow; no telemetry).

## Root Cause Analysis

### Investigation Tasks

- [x] Re-rate Priority and Effort at next /wr-itil:review-problems (2026-05-30: Impact 2 × Likelihood 3 = 6 (Medium), Effort S — one-character diff-filter change + test fixture extension; root cause + fix shape already documented, kept Open pending implementation)
- [x] Investigate root cause (`.husky/pre-commit` line 18: `git diff --cached --name-only --diff-filter=ACM` — the diff-filter literal excludes `R` per git diff-filter semantics; renamed files have status `R` and so are filtered out before prettier --write sees them)
- [x] Create reproduction test (`test/husky-pre-commit.test.js` — `[REQ-PRECOMMIT-AUTO-WRITE-RESTAGE] diff-filter includes R so rename-with-edit commits pass through auto-write (P018)` asserts `--diff-filter` literal contains `R`; fails RED on ACM, passes GREEN on ACMR)

## Fix Strategy

**Kind**: improve. **Shape**: shell script + test fixture.

**Target file**: `.husky/pre-commit` (the auto-write block) + `test/husky-pre-commit.test.js` (REQ-PRECOMMIT-AUTO-WRITE-RESTAGE assertions).

**Observed flaw**: `git diff --cached --name-only --diff-filter=ACM` excludes `R` (renamed). When a commit stages a rename-with-edit (e.g. `git mv old new` + Edit-tool change to the renamed file), the auto-write block skips the renamed file and `format:check` rejects the commit. P009's fix contract held for plain Modify shapes but not for rename-with-edit — a related-but-distinct gap.

**Edit summary**: change the diff-filter from `ACM` to `ACMR` so renames-with-edits pass through the auto-write step. Also extend `REQ-PRECOMMIT-AUTO-WRITE-RESTAGE` (`test/husky-pre-commit.test.js`) with an assertion covering the rename-with-edit case (stage a rename + post-rename Edit; commit; assert no format:check rejection AND the formatted content lands IN the commit). Routing target: this project's own `.husky/pre-commit` (local shell-script edit) + REQ-PRECOMMIT-AUTO-WRITE-RESTAGE test fixture.

**Evidence**:

- This session commit `c0dfae8` (run-retro session-wrap closing P009 + briefing refresh) was REJECTED on first try by `format:check` after auto-write skipped the renamed `docs/problems/closed/009-...md` (renamed-with-edit from `verifying/009-...md`).
- Recovery: manual `npm run format && git add ...` then retry — exactly the friction P009 was supposed to eliminate, but for the rename shape.
- The hook output explicitly listed only the README files (`docs/problems/README-history.md 12ms (unchanged)`, `docs/problems/README.md 9ms (unchanged)`) — the renamed file was NOT in the auto-write log, confirming the diff-filter ACM excludes R.

## Fix Released

Committed 2026-05-30. `.husky/pre-commit` line 18 now uses `--diff-filter=ACMR` instead of `ACM`; renamed-with-edit files pass through the auto-write block and the subsequent `format:check` succeeds on first try. ADR-0016 Confirmation criterion #2 updated to lock the new literal. REQ-PRECOMMIT-AUTO-WRITE-RESTAGE test suite extended with the new diff-filter-includes-R assertion — 5 / 5 passing GREEN. Awaiting user verification on the next rename-with-edit commit that the auto-write block no longer skips the renamed file.

## Dependencies

- **Blocks**: (none)
- **Blocked by**: (none)
- **Composes with**: P009 (closed) — same auto-write verification contract; this ticket extends coverage to rename-with-edit case

## Related

(captured via /wr-itil:capture-problem; expand at next investigation)

Duplicate-grep matches (informational; not true duplicates):

- `docs/problems/closed/009-edit-tool-markdown-writes-skip-prettier-pre-commit-format-check-fails.md` — closed; this ticket extends its REQ-PRECOMMIT-AUTO-WRITE-RESTAGE coverage to rename-with-edit
- `docs/problems/closed/003-pre-commit-prettier-leaves-unstaged-deltas.md` — closed; related historical context