docker-image-publish.yml

name: Publish Docker image

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

jobs:
  build:
    name: Docker image build and publish
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2

      - name: Build image
        run: |

          # The following AWK command removes first two parts of the value delimited by slash
          # As such, "ref/tags/1.0" becomes "1.0", but "ref/heads/feature/foo" becomes "feature/foo"
          export COW_VERSION=$(echo $GITHUB_REF | awk '{ n=split($0, parts, "/"); result = ""; for(i=3; i<=n; ++i){result = result "/" parts[i] }; print substr(result, 2) }')
          if [[ "$GITHUB_REF" == "refs/heads/"* ]] ; then
            COMPOSER_COW_VERSION="dev-$COW_VERSION";
          else
            COMPOSER_COW_VERSION="$COW_VERSION"
          fi

          # Log/Debug output
          echo "Building version: $COW_VERSION"

          # The next line preserves $COW_VERSION across the steps
          echo "COW_VERSION=$COW_VERSION" >> $GITHUB_ENV

          # Building a new image and tag it as "cow-image"
          docker build -t 'cow-image' --target stable --build-arg COW_VERSION=$COMPOSER_COW_VERSION - < docker/Dockerfile

      - name: Log into GitHub Packages registry
        run: |
          # The security token is issued automatically by GitHub for GitHub Actions of the same repository
          echo "${{ secrets.GITHUB_TOKEN }}" | docker login ghcr.io -u ${{ github.actor }} --password-stdin

      - name: Push image
        run: |

          if [[ "$GITHUB_REF" == "refs/heads/master" ]] ; then
            # If it's master, release a timestamp version
            IMAGE_ID=ghcr.io/${{ github.repository }}/master
            VERSION=$(date +%s)

          elif [[ "$GITHUB_REF" == "refs/tags/"* ]] ; then
            # If it's a tag, name it "release" and use the tag as the release version
            IMAGE_ID=ghcr.io/${{ github.repository }}/release
            VERSION=$COW_VERSION

          else
            # If it's a branch, use the branch name and timestamp as the version
            # WARNING: branch names out of [0-9a-z_-] won't work
            # Also, see "on.push.branches" rule at the top of this file (only whitelisted branches would get here)
            IMAGE_ID=ghcr.io/${{ github.repository }}/$COW_VERSION
            VERSION=$(date +%s)
          fi

          echo "Publishing $IMAGE_ID:$VERSION"
          docker tag cow-image $IMAGE_ID:$VERSION
          docker tag cow-image $IMAGE_ID:latest
          docker push $IMAGE_ID:$VERSION
          docker push $IMAGE_ID:latest