mergify-ready.yml

name: Pre-merge checks

on:
  pull_request:
    types:
      - opened
      - reopened
      - synchronize
      - converted_to_draft
      - ready_for_review
      - labeled
      - unlabeled
      - auto_merge_enabled
      - auto_merge_disabled
  merge_group:

jobs:
  wait-integration-pre-checks:
    runs-on: ubuntu-latest
    steps:
      - shell: bash
        run: echo "TODO remove this vestigial job"

  merge-strategy:
    runs-on: ubuntu-latest
    if: >-
      github.event_name != 'pull_request' ||
      github.event.pull_request.draft == true ||
      github.event.pull_request.base.ref != 'master' || (
        contains(github.event.pull_request.labels.*.name, 'automerge:squash') ||
        contains(github.event.pull_request.labels.*.name, 'automerge:no-update') ||
        contains(github.event.pull_request.labels.*.name, 'automerge:rebase') ||
        contains(github.event.pull_request.labels.*.name, 'bypass:automerge') ||
        github.event.pull_request.auto_merge != null
      )
    strategy:
      # abuse the matrix feature to create a check which stays pending until
      # a merge strategy is chosen
      matrix:
        merge: [chosen]
    steps:
      - shell: bash
        run: echo "Merge strategy chosen"

  linear-history:
    runs-on: ubuntu-latest
    if: >-
      github.event_name == 'pull_request' &&
      github.event.pull_request.draft == false &&
      github.event.pull_request.base.ref == 'master' && (
        contains(github.event.pull_request.labels.*.name, 'automerge:no-update') ||
        contains(github.event.pull_request.labels.*.name, 'bypass:automerge')
      ) &&
      !contains(github.event.pull_request.labels.*.name, 'bypass:linear-history')
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - shell: bash
        env:
          HEAD_SHA: ${{ github.event.pull_request.head.sha }}
          HEAD_LABEL: ${{ github.event.pull_request.head.label }}
          BASE_SHA: ${{ github.event.pull_request.base.sha }}
          BASE_LABEL: ${{ github.event.pull_request.base.label }}
        run: |
          merge_commits=$(git rev-list --merges "$BASE_SHA".."$HEAD_SHA")

          if [ -n "$merge_commits" ]; then
            echo "Error: merge commits found in $BASE_LABEL..$HEAD_LABEL"

            for merge_commit in $merge_commits; do
              echo "$merge_commit"
            done

            exit 1
          fi

          fixup_commits=
          for commit in $(git rev-list $BASE_SHA..$HEAD_SHA); do
            case $(git show --pretty=format:%s -s $commit) in fixup\!*|squash\!*|amend\!*)
              fixup_commits="$fixup_commits\n$commit"
              ;;
            esac
          done

          if [ -n "$fixup_commits" ]; then
            echo "Error: fixup/squash/amend commits found in $BASE_LABEL..$HEAD_LABEL"
            echo -e "$fixup_commits"
            exit 1
          fi

  no-fixup-commits:
    runs-on: ubuntu-latest
    if: >-
      github.event_name == 'pull_request' &&
      github.event.pull_request.draft == false &&
      github.event.pull_request.base.ref == 'master' && 
      contains(github.event.pull_request.labels.*.name, 'automerge:rebase') &&
      !contains(github.event.pull_request.labels.*.name, 'bypass:linear-history')

    env:
      HEAD_SHA: ${{ github.event.pull_request.head.sha }}
      BASE_SHA: ${{ github.event.pull_request.base.sha }}

    steps:
      - name: Checkout code
        uses: actions/checkout@v4
        with:
          fetch-depth: 0
      - name: Check for fixup commits
        id: fixup-commits
        run: |
          if ! git merge-base --is-ancestor "$BASE_SHA" "$HEAD_SHA"; then
             echo "PR is not up to date with target branch, skipping fixup commit check"
          elif [[ $(git rev-list "$BASE_SHA".."$HEAD_SHA" --grep="^\(fixup\|amend\|squash\)! " | wc -l) -eq 0 ]]; then
            echo "No fixup/amend/squash commits found in commit history"
          else
            echo "fixup/amend/squash commits found in commit history"
            exit 1
          fi