feat: attempt to sign and re-release on cron

.github/workflows/docker-build.yml

@@ -1,6 +1,8 @@
 name: Publish Docker image
 
 on:
+  schedule:
+    - cron: "24 0 * * 1"
   workflow_dispatch:
   push:
     branches:
@@ -20,25 +22,41 @@ jobs:
     permissions:
       contents: read
       packages: write
+      # This is used to complete the identity challenge
+      # with sigstore/fulcio when running outside of PRs.
+      id-token: write
 
     steps:
       - name: Checkout repository
         uses: actions/checkout@v3
+        with:
+          fetch-depth: 1
+
+      # Install the cosign tool except on PR
+      # https://github.com/sigstore/cosign-installer
+      - name: Install Cosign
+        if: github.event_name != 'pull_request'
+        uses: sigstore/cosign-installer@f3c664df7af409cb4873aa5068053ba9d61a57b6 #v2.6.0
+        with:
+          cosign-release: "v1.13.1"
 
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v2
 
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v2
 
-      - name: Log in to the Container registry
+      - name: Login to GitHub Container Registry
+        if: github.event_name != 'pull_request'
         uses: docker/login-action@v2
         with:
           registry: ghcr.io
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
-      - name: Extract metadata (tags, labels) for Docker
+      # Extract metadata (tags, labels) for Docker
+      # https://github.com/docker/metadata-action
+      - name: Extract Docker metadata
         id: meta
         uses: docker/metadata-action@v4
         with:
@@ -48,13 +66,31 @@ jobs:
             type=ref,event=pr
             type=semver,pattern={{version}}
             type=semver,pattern={{major}}.{{minor}}
-            type=sha
+            type=sha,format=long
 
-      - name: Build and push Docker image
+      # Build and push Docker image with Buildx (don't push on PR)
+      # https://github.com/docker/build-push-action
+      - name: Build and Push container images
         uses: docker/build-push-action@v4
+        id: build-and-push
         with:
           context: .
           platforms: linux/amd64,linux/arm64
-          push: true
+          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
+
+      # Sign the resulting Docker image digest except on PRs.
+      # This will only write to the public Rekor transparency log when the Docker
+      # repository is public to avoid leaking data.  If you would like to publish
+      # transparency data even for private images, pass --force to cosign below.
+      # https://github.com/sigstore/cosign
+      - name: Sign the published Docker image
+        if: ${{ github.event_name != 'pull_request' }}
+        env:
+          COSIGN_EXPERIMENTAL: "true"
+        # This step uses the identity token to provision an ephemeral certificate
+        # against the sigstore community Fulcio instance.
+        run: echo "${{ steps.meta.outputs.tags }}" | xargs -I {} cosign sign {}@${{ steps.build-and-push.outputs.digest }}