Contributor guides now match what the hook enforces so failures are obvious
before push when core.hooksPath points at .githooks.
- Refresh commit.prompt.md hook bullets and the canonical message checklist
- Update AGENTS.md workflow paragraph for commit-msg structure plus line cap
Long commit subjects and bullets are hard to read in narrow terminals and
mailed logs. Contributors using `.githooks` via core.hooksPath now get an
automatic guard in addition to the two-file pre-commit cap.
- Add `.githooks/commit-msg` to fail when any message line exceeds 80 chars
- Skip length checks while `.git/MERGE_HEAD` exists for merge commits
- Sync AGENTS.md, README.md, CONTRIBUTING.md, and commit.prompt.md
Introduce `.github/prompts/commit.prompt.md` as the contributor-facing description
of how assistants should stage, review, propose, and record commits.
- Document defaults: one file per commit, rare justified pairs, no blanket `git add`.
- Describe optional `.githooks/pre-commit` cap at two staged paths.
- Require reading the full `git diff --staged` (no truncation) before messaging.
- Spell out approval-before-commit flow and Conventional Commits subject lines.
- Scale the body to the patch: short summaries for small edits; large or
multi-concern diffs need grouped, substantive bullets so history stays readable.
- Keep checklist items aligned with that depth expectation.
Jukka Aho