docker-build-fork.yml

name: Docker Build (Fork)
on:
  pull_request:
jobs:
  docker-build-succeeds:
    runs-on: ubuntu-latest
    if: ${{ github.event.pull_request.head.repo.fork }}
    steps:
      - name: Checkout
        uses: actions/checkout@v3
        with:
          fetch-depth: 0
      - name: Docker Build
        run: docker build . --no-cache