build: add tags and multi-registry push to distributed gha example

content/manuals/build/ci/github-actions/multi-platform.md

@@ -109,7 +109,10 @@ each platform across multiple runners and create manifest list using the
 
 The following workflow will build the image for each platform on a dedicated
 runner using a matrix strategy and push by digest. Then, the `merge` job will
-create a manifest list and push it to Docker Hub.
+create manifest lists and push them to two registries:
+
+- Docker Hub: `docker.io/docker-user/my-app`
+- GitHub Container Registry: `ghcr.io/gh-user/my-app`
 
 This example also uses the [`metadata` action](https://github.com/docker/metadata-action)
 to set tags and labels.
@@ -121,7 +124,8 @@ on:
   push:
 
 env:
-  REGISTRY_IMAGE: user/app
+  DOCKERHUB_REPO: docker-user/my-app
+  GHCR_REPO: ghcr.io/gh-user/my-app
 
 jobs:
   build:
@@ -131,8 +135,6 @@ jobs:
       matrix:
         platform:
           - linux/amd64
-          - linux/arm/v6
-          - linux/arm/v7
           - linux/arm64
     steps:
       - name: Prepare
@@ -144,14 +146,23 @@ jobs:
         id: meta
         uses: docker/metadata-action@v5
         with:
-          images: ${{ env.REGISTRY_IMAGE }}
+          images: |
+            ${{ env.DOCKERHUB_REPO }}
+            ${{ env.GHCR_REPO }}
 
       - name: Login to Docker Hub
         uses: docker/login-action@v3
         with:
           username: ${{ vars.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
 
+      - name: Login to GHCR
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
       - name: Set up QEMU
         uses: docker/setup-qemu-action@v3
 
@@ -164,7 +175,7 @@ jobs:
         with:
           platforms: ${{ matrix.platform }}
           labels: ${{ steps.meta.outputs.labels }}
-          outputs: type=image,name=${{ env.REGISTRY_IMAGE }},push-by-digest=true,name-canonical=true,push=true
+          outputs: type=image,"name=${{ env.DOCKERHUB_REPO }},${{ env.GHCR_REPO }}",push-by-digest=true,name-canonical=true,push=true
 
       - name: Export digest
         run: |
@@ -198,24 +209,41 @@ jobs:
           username: ${{ vars.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
 
+      - name: Login to GHCR
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
 
       - name: Docker meta
         id: meta
         uses: docker/metadata-action@v5
         with:
-          images: ${{ env.REGISTRY_IMAGE }}
+          images: |
+            ${{ env.DOCKERHUB_REPO }}
+            ${{ env.GHCR_REPO }}
+          tags: |
+            type=ref,event=branch
+            type=ref,event=pr
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
 
       - name: Create manifest list and push
         working-directory: /tmp/digests
         run: |
           docker buildx imagetools create $(jq -cr '.tags | map("-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
-            $(printf '${{ env.REGISTRY_IMAGE }}@sha256:%s ' *)
+            $(printf '${{ env.DOCKERHUB_REPO }}@sha256:%s ' *)
+          docker buildx imagetools create $(jq -cr '.tags | map("-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
+            $(printf '${{ env.GHCR_REPO }}@sha256:%s ' *)
 
       - name: Inspect image
         run: |
-          docker buildx imagetools inspect ${{ env.REGISTRY_IMAGE }}:${{ steps.meta.outputs.version }}
+          docker buildx imagetools inspect ${{ env.DOCKERHUB_REPO }}:${{ steps.meta.outputs.version }}
+          docker buildx imagetools inspect ${{ env.GHCR_REPO }}:${{ steps.meta.outputs.version }}
 ```
 
 ### With Bake