build-test.yml

name: Docker Image Build

on:
  push:
    branches: [ master ]
    paths:
      - '*/Dockerfile'
  pull_request:
    branches: [ master ]
    paths:
      - '*/Dockerfile'

jobs:
  files:
    runs-on: ubuntu-latest

    outputs:
      matrix: ${{ steps.dockerfile.outputs.matrix }}

    steps:
    - name: Checkout repository
      uses: actions/checkout@v2
      with:
        fetch-depth: 0

    - name: Get changed files
      id: files
      uses: jitterbit/get-changed-files@v1
      with:
        format: json

    - name: Extract Dockerfile files
      id: dockerfile
      run: |
        FILES=$( echo '${{ steps.files.outputs.added_modified }}' | jq -c 'map(select(. | endswith("Dockerfile")))' )
        echo "::set-output name=matrix::$FILES"

  build:
    runs-on: ubuntu-latest
    needs: files
    
    strategy:
      fail-fast: false
      matrix:
        dockerfile: ${{ fromJSON(needs.files.outputs.matrix) }}

    steps:
    - name: Checkout repository
      uses: actions/checkout@v2

    - name: Build Docker image ${{ matrix.dockerfile }}
      run: |
        cd "$(dirname ${{ matrix.dockerfile }})"
        docker build . --file Dockerfile