ci: improve docker action

.github/workflows/publish_image.yaml

@@ -1,46 +1,83 @@
 ---
 name: "Publish Docker Image"
 
-permissions:
-  packages: write
-  contents: read
-  attestations: write
-  id-token: write
-
 env:
-  OAK_MODULE_DIR: "code/oak-d-lite-module"
   REGISTRY: "ghcr.io"
   IMAGE_NAME: "${{ github.repository }}:latest"
 
 on:
   push: # Only run after merge to main, when these files change
-    branches: [master, main]
+    branches: [$default-branch]
     paths:
       - "code/oak-d-lite-module/Dockerfile"
       - "code/oak-d-lite-module/requirements.txt"
       - "code/oak-d-lite-module/vision_webserver.py"
       - ".github/workflows/publish_image.yaml" # This file
+    # Publish semver tags as releases.
+    tags: ["v*.*.*"]
+  pull_request:
+    branches: [$default-branch]
   workflow_dispatch:
 
 jobs:
   build:
     name: Publish Docker Image
     runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+      id-token: write
+      attestations: write
+
     steps:
       - name: Checkout Code
         uses: actions/checkout@v4
         with:
           fetch-depth: 0
 
-      - name: Log into GHCR
-        run: docker login "${{ env.REGISTRY }}" -u "${{ github.repository_owner }}" --password "${{ secrets.GITHUB_TOKEN }}"
+      - name: Install cosign
+        if: github.event_name != 'pull_request'
+        uses: sigstore/cosign-installer@59acb6260d9c0ba8f4a2f9d9b48431a222b68e20 #v3.5.0
+        with:
+          cosign-release: "v2.2.4"
 
-      - name: Build Docker Image
-        run: |
-          pushd "$OAK_MODULE_DIR"
-          docker build -t "${{ env.IMAGE_NAME }}" .
-          popd
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3.0.0
+
+      # 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@v3.0.0
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract Docker metadata
+        id: meta
+        uses: docker/metadata-action@v5.0.0
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+
+      - name: Build and push Docker image
+        id: build-and-push
+        uses: docker/build-push-action@v5.0.0
+        with:
+          context: .
+          push: ${{ github.event_name != 'pull_request' }} # Don't push on PR
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
 
-      - name: Push Docker Image
-        run: docker push "${{ env.IMAGE_NAME }}"
+      - name: Sign the published Docker image
+        if: ${{ github.event_name != 'pull_request' }}
+        env:
+          # https://docs.github.com/en/actions/security-guides/security-hardening-for-github-actions#using-an-intermediate-environment-variable
+          TAGS: ${{ steps.meta.outputs.tags }}
+          DIGEST: ${{ steps.build-and-push.outputs.digest }}
+        # This step uses the identity token to provision an ephemeral certificate
+        # against the sigstore community Fulcio instance.
+        run: echo "${TAGS}" | xargs -I {} cosign sign --yes {}@${DIGEST}
 # EOF