name: First commit message adheres to guidelines

on: [pull_request]

env:
  NODE_VERSION: lts/*

permissions:
  contents: read

jobs:
  lint-commit-message:
    runs-on: ubuntu-latest
    steps:
      - name: Compute number of commits in the PR
        id: nb-of-commits
        run: |
          echo "plusOne=$((${{ github.event.pull_request.commits }} + 1))" >> $GITHUB_OUTPUT
          echo "minusOne=$((${{ github.event.pull_request.commits }} - 1))" >> $GITHUB_OUTPUT
      - uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9  # v3.5.3
        with:
          fetch-depth: ${{ steps.nb-of-commits.outputs.plusOne }}
          persist-credentials: false
      - run: git reset HEAD^2
      - name: Install Node.js
        uses: actions/setup-node@e33196f7422957bea03ed53f6fbb155025ffc7b8  # v3.7.0
        with:
          node-version: ${{ env.NODE_VERSION }}
      - name: Validate commit message
        run: |
          echo "::add-matcher::.github/workflows/commit-lint-problem-matcher.json"
          git rev-parse HEAD~${{ steps.nb-of-commits.outputs.minusOne }} | xargs npx -q core-validate-commit --no-validate-metadata --tap