headroom/.pre-commit-config.yaml
Rick van Hattem db0356b0e7
ci: guard against committed merge-conflict markers (#1505)
## Description

Prevent unresolved Git merge-conflict markers from ever being merged
again. `CHANGELOG.md` collected literal `<<<<<<<` / `=======` /
`>>>>>>>` lines from **two** separate merged PRs (removed in #1497) and
nothing caught them: no `check-merge-conflict` hook, no workflow runs
`pre-commit`, and `ruff`/`mypy`/`pytest` do not parse Markdown.

This adds two layers:

1. **Dedicated `merge-conflicts` workflow**
(`.github/workflows/merge-conflicts.yml`) — runs on every PR/push, greps
all tracked files for conflict markers, and fails with the offending
locations. It is a **standalone workflow on purpose**: `ci.yml` sets
`on.pull_request.paths-ignore: ['**/*.md', ...]`, so a
Markdown/CHANGELOG-only PR skips `ci.yml` entirely — and the markers
this guard exists to catch landed in `CHANGELOG.md`. The new workflow
has no `paths-ignore`, so it always runs. (Thanks to the automated
review for catching that an earlier revision put the job inside
`ci.yml`, which would have reproduced the gap.)
2. **`check-merge-conflict` pre-commit hook** (`--assume-in-merge`) — a
local early-catch for devs who install hooks. The workflow is the actual
enforcement since hooks are opt-in.

## Type of Change

- [x] Bug fix (non-breaking change that fixes an issue)
- [ ] New feature (non-breaking change that adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update
- [ ] Performance improvement
- [ ] Code refactoring (no functional changes)

## Changes Made

- `.github/workflows/merge-conflicts.yml` (new): a single
`merge-conflicts` job, **no `paths-ignore`**, that runs `git grep -nI -E
'^(<{7}|>{7}|\|{7})( |$)'` over all tracked files and fails if any
match. Matches conflict start/end (and diff3 `|||||||`) markers — every
real conflict has these — while deliberately not matching a bare
`=======`, to avoid false positives on Markdown setext headers.
- `.pre-commit-config.yaml`: add `pre-commit/pre-commit-hooks`
`check-merge-conflict` with `--assume-in-merge`.

## Testing

- [x] Linting passes (`actionlint`)
- [x] Manual testing performed
- [ ] Unit tests pass (`pytest`) — N/A, CI-config + pre-commit change
(no product code)
- [ ] Type checking passes (`mypy headroom`) — N/A
- [ ] New tests added for new functionality — N/A (the guard is itself
the test; verified below)

### Test Output

```text
# The guard's command catches real markers (run against the pre-#1497 tree that still had them):
$ git grep -nI -E '^(<{7}|>{7}|\|{7})( |$)' <markered-tree> -- .
CHANGELOG.md:11:<<<<<<< pr/503-proactive-expansion-xml-tag
CHANGELOG.md:19:>>>>>>> main
CHANGELOG.md:48:<<<<<<< fix/gemini-offload
CHANGELOG.md:53:>>>>>>> main
#  -> exit 0 (matches found) => workflow step exits 1 (fails)

# And passes on a clean tree (this branch):
$ git grep -nI -E '^(<{7}|>{7}|\|{7})( |$)' HEAD -- .
#  (no output) -> exit 1 (no matches) => prints "No merge-conflict markers found." and exits 0

$ actionlint .github/workflows/merge-conflicts.yml .github/workflows/ci.yml  -> (no output) exit 0
$ commitlint --from <base> --to HEAD                                          -> 0 problems, 0 warnings
# Both workflow YAMLs parse; merge-conflicts.yml has no `paths-ignore`, so it runs on Markdown-only PRs.
```

## Real Behavior Proof

- Environment: Linux; the repo at this branch
(`ci/guard-merge-conflict-markers`), with `actionlint 1.7.7` and
`commitlint` (`@commitlint/config-conventional`). The "real behavior"
under test is the workflow's grep command and the YAML/trigger config —
exercised directly, not mocked.
- Exact command / steps: ran the workflow's exact command (`git grep -nI
-E '^(<{7}|>{7}|\|{7})( |$)' -- .`) against a tree that contains markers
and against this clean branch; ran `actionlint` on both workflow files;
parsed `merge-conflicts.yml` and confirmed its `pull_request` trigger
has no `paths-ignore` (the fix for the Markdown-only gap).
- Observed result: against the markered tree the command matched the
conflict start/end lines and exited 0 → the job exits 1 (red); against
this branch it matched nothing and exited 1 → the job prints "No
merge-conflict markers found." and exits 0 (green). `actionlint`
reported no problems on either workflow, and `merge-conflicts.yml` is
confirmed to omit `paths-ignore`, so it runs on CHANGELOG-only PRs that
`ci.yml` skips.
- Not tested: I did not drive the `check-merge-conflict` pre-commit hook
through a real in-progress merge (it is a standard upstream hook); the
gated CI run (fork-PR approval) was not executed — the guard logic and
triggers are verified above.

## Review Readiness

- [x] I have performed a self-review
- [x] This PR is ready for human review

## Checklist

- [x] My code follows the project's style guidelines
- [x] I have performed a self-review of my code
- [x] I have commented my code, particularly in hard-to-understand areas
- [x] I have made corresponding changes to the documentation (inline
comments explain the workflow + hook)
- [x] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works (the guard is self-verifying; see Real Behavior Proof)
- [x] New and existing unit tests pass locally with my changes
- [ ] I have updated the CHANGELOG.md if applicable (N/A — CI tooling,
no user-facing change)

## Additional Notes

- **Supply chain:** the only new dependency is the
`pre-commit/pre-commit-hooks` repo pinned at `v5.0.0`. It is the
canonical pre-commit hooks collection maintained by the pre-commit
author (Anthony Sottile), is dev-only (runs solely inside pre-commit),
contains no native code, and has no runtime/install-time footprint. The
repo already trusts `astral-sh/ruff-pre-commit` and
`pre-commit/mirrors-mypy` the same way.
- The workflow adds ~10s per run and needs no secrets, network, or
build. Rebased onto current `main` after #1497 merged, so this is now a
clean single commit (the changelog cleanup is already on `main`).
2026-06-30 14:20:25 -05:00

38 lines
1.3 KiB
YAML

repos:
- repo: local
hooks:
- id: sync-plugin-versions
name: Sync plugin versions
entry: python3 scripts/sync-plugin-versions.py
language: system
pass_filenames: false
always_run: true
- id: commitlint
name: Commitlint
entry: bash -lc 'npx --yes --package=@commitlint/cli --package=@commitlint/config-conventional -- commitlint --edit "$1" --config .commitlintrc.json' --
language: system
stages: [commit-msg]
- repo: https://github.com/pre-commit/pre-commit-hooks
rev: v5.0.0
hooks:
- id: check-merge-conflict
# Catch markers even outside an in-progress merge (e.g. committing a
# botched conflict resolution from a rebase). CI re-checks this
# unconditionally, so installing hooks is not required for enforcement.
args: [--assume-in-merge]
- repo: https://github.com/astral-sh/ruff-pre-commit
rev: v0.9.4
hooks:
- id: ruff
args: [--fix]
exclude: ^experiments/
- id: ruff-format
exclude: ^experiments/
- repo: https://github.com/pre-commit/mirrors-mypy
rev: v1.14.1
hooks:
- id: mypy
args: [--ignore-missing-imports]
exclude: ^experiments/
pass_filenames: false
entry: mypy headroom