New approach with pushing the images in any case and retagging them once the test is complete.

Author: Morl99

.github/workflows/build-and-publish.yml

@@ -1,10 +1,5 @@
 name: Docker
 
-# This workflow uses actions that are not certified by GitHub.
-# They are provided by a third-party and are governed by
-# separate terms of service, privacy policy, and support
-# documentation.
-
 on:
   schedule:
     - cron: '18 2 * * *'
@@ -17,7 +12,6 @@ env:
   REGISTRY: ghcr.io
   IMAGE_NAME: dbsystel/postgresql-partman
 
-
 jobs:
   build:
     strategy:
@@ -40,26 +34,22 @@ 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@v4
 
       # 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@v3.4.0
 
-      # Workaround: https://github.com/docker/build-push-action/issues/461
+      # Workaround for Docker buildx issue
       - 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
@@ -69,7 +59,6 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
 
       # Extract metadata (tags, labels) for Docker
-      # https://github.com/docker/metadata-action
       - name: Extract Docker metadata
         id: meta
         uses: docker/metadata-action@v5
@@ -80,8 +69,7 @@ jobs:
             type=raw,value=${{ matrix.postgres_version }},enable=${{ matrix.default == 'true'}}
             ${{ matrix.postgres_version }}-${{ matrix.major }}
 
-      # Build and push Docker image with Buildx (don't push on PR)
-      # https://github.com/docker/build-push-action
+      # Build and push Docker image with Buildx, using only the digest
       - name: Build and push Docker image
         id: build-and-push
         uses: docker/build-push-action@v5
@@ -92,22 +80,43 @@ jobs:
             PARTMAN_VERSION=${{ matrix.partman_version }}
             PARTMAN_CHECKSUM=${{ matrix.partman_checksum }}
           platforms: linux/amd64,linux/arm64
-          push: ${{ github.event_name != 'pull_request' }}
-          tags: ${{ steps.meta.outputs.tags }}
+          outputs: type=docker
+          push: true
           labels: ${{ steps.meta.outputs.labels }}
           cache-from: type=gha
           cache-to: type=gha,mode=max
 
+      # Test the built Docker image using the digest
+      - name: Test Docker image
+        env:
+          POSTGRES_PASSWORD: examplepassword
+        run: |
+          DIGEST=${{ steps.build-and-push.outputs.digest }}
+          docker run -d --name test-db -e POSTGRES_PASSWORD=$POSTGRES_PASSWORD ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}@$DIGEST
+          sleep 30
+          docker exec test-db pg_isready -U postgres
+          docker stop test-db
+          docker rm test-db
+
+      # Retag and push Docker image after successful tests
+      - name: Retag and push Docker image
+        if: github.event_name != 'pull_request'
+        run: |
+          DIGEST=${{ steps.build-and-push.outputs.digest }}
+          TAGS=$(echo ${{ steps.meta.outputs.tags }} | tr ',' '\n')
+          for TAG in $TAGS; do
+            docker tag ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}@$DIGEST ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:$TAG
+            docker push ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:$TAG
+          done
 
-      # 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 ev en for private images, pass --force to cosign below.
-      # https://github.com/sigstore/cosign
+      # Sign the resulting Docker image digest except on PRs
       - name: Sign the published Docker image
-        if: ${{ github.event_name != 'pull_request' }}
+        if: github.event_name != 'pull_request'
         env:
           COSIGN_EXPERIMENTAL: "true"
-        # This step uses the identity token to provision an ephemeral certificate
-        # against the sigstore community Fulcio instance.
-        run: echo "${{ steps.meta.outputs.tags }}" | xargs -I {} cosign sign -y {}@${{ steps.build-and-push.outputs.digest }}
+        run: |
+          DIGEST=${{ steps.build-and-push.outputs.digest }}
+          TAGS=$(echo ${{ steps.meta.outputs.tags }} | tr ',' '\n')
+          for TAG in $TAGS; do
+            cosign sign -y ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:$TAG
+          done