image.yaml

name: Build Docker Image

on:
  workflow_dispatch:
  push:
    branches:
      - main
    tags:
      - v*
  pull_request:
    branches:
      - main

jobs:
  build:
    name: Build Docker Image
    runs-on: ubuntu-latest
    permissions:
      contents: read
      packages: write
    env:
      CAN_PUSH: ${{ github.event_name != 'pull_request' && github.actor == github.repository_owner }}
    steps:
      - uses: actions/checkout@v5
      - name: Generate Image Tags
        uses: docker/metadata-action@v5
        id: meta
        with:
          images: ghcr.io/${{ github.repository }}
      - name: Login to GitHub Container Registry
        if: env.CAN_PUSH
        uses: docker/login-action@v3
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}
      - name: Build and push
        uses: docker/build-push-action@v6
        with:
          context: .
          push: ${{ env.CAN_PUSH }}
          platforms: linux/amd64
          tags: ${{ steps.meta.outputs.tags }}
          labels: ${{ steps.meta.outputs.labels }}

  # deploy branch にビルド済みの Docker image を参照する Dockerfile を作成するJob
  # deploy という名前の orphan branch が事前に作られている必要がある
  #
  # ```sh
  # git switch --orphan deploy
  # git rm -rf .
  # git push HEAD:deploy
  # ```
  #
  # deploy:
  #   name: Deploy
  #   runs-on: ubuntu-latest
  #   needs: build
  #   if: github.event_name != 'pull_request'
  #   permissions:
  #     contents: write
  #   steps:
  #     - uses: actions/checkout@v5
  #       with:
  #         ref: deploy
  #     - name: Create Dockerfile for deploy
  #       run: printf "%s\n" "$DOCKERFILE" > Dockerfile
  #       env:
  #         DOCKERFILE: |
  #           FROM ghcr.io/${{ github.repository }}:${{ github.sha }}
  #           # 必要に応じて設定を追加する
  #     - name: Push empty commit
  #       run: |
  #         git config user.name "GitHub Actions"
  #         git config user.email "actions@github.com"
  #         git add Dockerfile
  #         git commit -m "Trigger deploy: ${{ github.ref }}"
  #         git push origin HEAD:deploy
  #       env:
  #         GITHUB_TOKEN: ${{ github.token }}
  #