name: Pull Request
on:
  pull_request:
    types:
      - labeled
      - opened
      - reopened
      - synchronize
      - unlabeled

jobs:
  linear-history:
    if: ${{ !contains(github.event.pull_request.labels.*.name, 'pr-permit-nonlinear') }}
    name: Linear History
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - name: No new merge commits
        run: |
          log() { printf %s\\n "$*" >&2; }
          error() { log "ERROR: $@"; }
          fatal() { error "$@"; exit 1; }
          try() { log "Running command $@"; "$@" || fatal "'$@' failed"; }
          out=$(try git rev-list -n 1 --merges '${{ github.event.pull_request.base.sha }}..${{ github.event.pull_request.head.sha }}') || exit 1
          [ -z "${out}" ] || {
              error "pull request includes a merge commit and does not have the 'pr-permit-nonlinear' label"
              git show "${out}" >&2
              exit 1
          }
  no-autosquash:
    if: ${{ !contains(github.event.pull_request.labels.*.name, 'pr-permit-autosquash') }}
    name: No --autosquash commits
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - name: 'No commits with messages starting with "fixup!", "squash!", or "amend!"'
        run: |
          log() { printf %s\\n "$*" >&2; }
          error() { log "ERROR: $@"; }
          fatal() { error "$@"; exit 1; }
          try() { log "Running command $@"; "$@" || fatal "'$@' failed"; }
          out=$(try git log --oneline '${{ github.event.pull_request.base.sha }}..${{ github.event.pull_request.head.sha }}') || exit 1
          ! grep -E '^[^ ]* (fixup|squash|amend)!' <<EOF || fatal "--autosquash commits not allowed without the 'pr-permit-autosquash' label"
          ${out}
          EOF