docker.yml

name: Docker Release

on:
  push:
    tags:
      - '*'
    branches:
      - master

permissions:
  contents: read

jobs:
  init:
    permissions:
      contents: none
    runs-on: ubuntu-latest
    outputs:
      do_docker: ${{ steps.vars.outputs.IS_DOCKERHUB_PUSH }}
    steps:
      - name: Initialize workflow variables
        shell: bash
        run: |
          # work-around for inaccessible 'secrets' object for 'if'; see <https://git.luolix.topmunity/t5/GitHub-Actions/jobs-lt-job-id-gt-if-does-not-work-with-env-secrets/m-p/38549>)
          unset IS_DOCKERHUB_PUSH
          if [ -z "$DOCKERHUB_PUSH" ]; then IS_DOCKERHUB_PUSH='false'; else IS_DOCKERHUB_PUSH='true' ; fi
          echo set-output name=IS_DOCKERHUB_PUSH::${IS_DOCKERHUB_PUSH}
          echo ::set-output name=IS_DOCKERHUB_PUSH::${IS_DOCKERHUB_PUSH}
        env:
          DOCKERHUB_PUSH: ${{ secrets.DOCKERHUB_PUSH }}
  build:
    name: Build and push Docker image
    runs-on: ubuntu-latest
    needs: [init]
    if: ${{ needs.init.outputs.do_docker == 'true' }}
    steps:
      - name: Checkout
        uses: actions/checkout@v2

      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v1

      - name: Login to DockerHub
        uses: docker/login-action@v1
        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_PASSWORD }}

      - name: Build and push latest
        uses: docker/build-push-action@v2
        if: github.ref == 'refs/heads/master'
        with:
          push: true
          tags: ${{ secrets.DOCKERHUB_REPO }}:latest

      - name: Set version variable
        id: version
        if: startsWith(github.ref, 'refs/tags/')
        run: echo ::set-output name=TAG::${GITHUB_REF#refs/tags/}

      - name: Build and push tag
        uses: docker/build-push-action@v2
        if: startsWith(github.ref, 'refs/tags/')
        with:
          push: true
          tags: ${{ secrets.DOCKERHUB_REPO }}:${{ steps.version.outputs.TAG }}