preview-build.yml

name: 🔬 Preview build

# Manual-dispatch image build for testing branches before they land on dev.
# Triggering on `fix/abort-kills-merge-and-cleanup-race` publishes
# `ghcr.io/mpecan/gha-cache-server:preview-<short-sha>` so a downstream
# deployment can pin it by digest. No lint/test gate — this is explicitly
# for in-cluster validation of in-flight patches; the full CI still runs on
# push and on the eventual PR.

on:
  workflow_dispatch:
    inputs:
      tag-suffix:
        description: "Optional extra tag suffix (appended after the short sha)"
        required: false
        default: ""

concurrency:
  group: preview-build-${{ github.ref }}
  cancel-in-progress: true

jobs:
  build:
    name: 🚀 Build and push preview
    permissions:
      packages: write
      contents: read
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v6

      - name: Compute tags
        id: tags
        run: |
          SHORT_SHA=$(git rev-parse --short HEAD)
          BRANCH_SLUG=$(echo "${{ github.ref_name }}" | tr '/' '-')
          SUFFIX="${{ inputs.tag-suffix }}"
          TAGS="ghcr.io/${{ github.repository }}:preview-${SHORT_SHA}"
          TAGS="${TAGS}
          ghcr.io/${{ github.repository }}:preview-${BRANCH_SLUG}"
          if [ -n "${SUFFIX}" ]; then
            TAGS="${TAGS}
          ghcr.io/${{ github.repository }}:preview-${SHORT_SHA}-${SUFFIX}"
          fi
          {
            echo "tags<<EOF"
            echo "$TAGS"
            echo "EOF"
            echo "short_sha=${SHORT_SHA}"
          } >> "$GITHUB_OUTPUT"

      - name: Login to GitHub Container Registry
        uses: docker/login-action@v4
        with:
          registry: ghcr.io
          username: ${{ github.actor }}
          password: ${{ secrets.GITHUB_TOKEN }}

      - name: Set up QEMU
        uses: docker/setup-qemu-action@v4

      - name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v4

      - name: Build and push
        id: build
        uses: docker/build-push-action@v7
        with:
          context: .
          platforms: linux/amd64,linux/arm64
          push: true
          tags: ${{ steps.tags.outputs.tags }}
          build-args: |
            BUILD_HASH=${{ steps.tags.outputs.short_sha }}

      - name: Print digest
        run: |
          echo "Image digest: ${{ steps.build.outputs.digest }}"
          echo
          echo "Pin in a deployment with:"
          echo "  image: ghcr.io/${{ github.repository }}@${{ steps.build.outputs.digest }}"