Check if PR is missing formatting

swiftformat-github-action.yml

name: auto-format
on: pull_request
jobs:
  format:
    # Check if the PR is not from a fork
    if: github.event.pull_request.head.repo.full_name == github.repository
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
        with:
          ref: ${{ github.head_ref }}
      - name: Login to GitHub Container Registry
        uses: docker/login-action@v2
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}
      - name: Run SwiftFormat
        id: git-check
        run: |
          docker pull ghcr.io/nicklockwood/swiftformat:latest
          docker run --rm -v ${{ github.workspace }}:/work -w /work ghcr.io/nicklockwood/swiftformat:latest "**/*.swift"
          echo ::set-output name=modified::$(if git diff-index --quiet HEAD --; then echo "false"; else echo "true"; fi)
      - name: Check code formatting status
        if: steps.git-check.outputs.modified == 'true'
        run: |
          echo "::error::Code need formatting (run swiftformat)"
          exit 1