Add GitHub Actions for Docker image

- Enable GitHub Actions Docker build cache
- Disable build cache for tags
- Allow running on dispatch without cache
- Push to ghcr.io on master branch and tags
- Publish build provenance attestation

.github/workflows/docker.yml

@@ -0,0 +1,90 @@
+name: docker
+on:
+  push:
+    branches:
+      - 'master'
+    tags:
+      - 'v*.*.*'
+  pull_request:
+    types:
+      - opened
+      - synchronize
+  workflow_dispatch:
+    inputs:
+      use_cache:
+        description: "Use build cache"
+        required: true
+        type: boolean
+        default: true
+
+env:
+  REGISTRY: ghcr.io
+  # ghrc.io/OWNER/REPO
+  IMAGE_NAME: ${{ github.repository }}
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+      id-token: write
+      attestations: write
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      # Workaround: https://github.com/docker/build-push-action/issues/461
+      - name: Setup Docker buildx
+        uses: docker/setup-buildx-action@v3
+
+      # Login against a Docker registry except on PR
+      # https://github.com/docker/login-action
+      - name: Log into registry ${{ env.REGISTRY }}
+        if: github.event_name != 'pull_request'
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      # Extract metadata (tags, labels) for Docker
+      # For some reason the title have to be set manually
+      # https://github.com/docker/metadata-action
+      - name: Extract Docker metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          labels: |
+            org.opencontainers.image.title=Oxipng
+
+      # Build and push Docker image with Buildx (don't push on PR)
+      # Cache isn't used for tags and on workflow_dispatch if specified
+      # https://github.com/docker/build-push-action
+      - name: Build and push Docker image
+        id: build-and-push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          platforms: linux/amd64,linux/arm64
+          push: ${{ github.event_name != 'pull_request' }}
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+          no-cache: ${{ (github.event_name == 'workflow_dispatch' && !inputs.use_cache) || startsWith(github.ref, 'refs/tags/') }}
+
+      # Attest the build provenance
+      # TODO: enable push to registry when referrers API will be supported by ghcr.io
+      - name: Attest Build Provenance
+        if: github.event_name != 'pull_request'
+        uses: actions/attest-build-provenance@v1
+        with:
+          subject-name: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          subject-digest: ${{ steps.build-and-push.outputs.digest }}
+          push-to-registry: false