ci: add arm64 container image build

.github/workflows/_prepare-image-build.yml

@@ -0,0 +1,23 @@
+name: Prepare building Docker image
+
+on:
+  workflow_call:
+    inputs:
+      registry:
+        required: true
+        type: string
+
+jobs:
+  prepare-image-build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@c47758b77c9736f4b2ef4073d4d51994fabfe349
+
+      # Uses the `docker/login-action` action to log in to the Container registry registry using the account and password that will publish the packages. Once published, the packages are scoped to the account defined here.
+      - name: Log in to the Container registry
+        uses: docker/login-action@65b78e6e13532edd9afa3aa52ac7964289d1a9c1
+        with:
+          registry: ${{ inputs.registry }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/docker-image.yml

@@ -3,6 +3,7 @@ name: Create and publish a Docker image
 # Configures this workflow to run every time a change is pushed to the branch called `main` or a tag named 'v*' is pushed.
 
 on:
+  workflow_dispatch:
   push:
     branches: ['main']
     tags:
@@ -15,17 +16,20 @@ env:
 
 # There is a single job in this workflow. It's configured to run on the latest available version of Ubuntu.
 jobs:
-  image:
-    runs-on: ubuntu-latest
+  build-image:
+    strategy:
+      fail-fast: false
+      matrix:
+        base-image: [debian, alpine]
+        platform: [linux/amd64, linux/arm64]
+
+    runs-on: ${{ matrix.platform == 'linux/arm64' && 'linux-arm64' || 'ubuntu-latest'  }}
+
     # Sets the permissions granted to the `GITHUB_TOKEN` for the actions in this job.
     permissions:
       contents: read
       packages: write
 
-    strategy:
-      fail-fast: false
-      matrix:
-        base-image: [debian, alpine]
     steps:
       - name: Prepare
         run: |
@@ -37,36 +41,90 @@ jobs:
             echo "FLAVOR_OPTS=suffix=-alpine,onlatest=true" >> $GITHUB_ENV
           fi
 
+          platform=${{ matrix.platform }}
+          echo "PLATFORM_PAIR=${platform//\//-}" >> $GITHUB_ENV
+
       - name: Checkout repository
         uses: actions/checkout@v4
-      # Uses the `docker/login-action` action to log in to the Container registry registry using the account and password that will publish the packages. Once published, the packages are scoped to the account defined here.
-      - name: Log in to the Container registry
-        uses: docker/login-action@65b78e6e13532edd9afa3aa52ac7964289d1a9c1
+
+      - name: Prepare Docker image build
+        uses: ./.github/workflows/_prepare-image-build.yml
         with:
           registry: ${{ env.REGISTRY }}
-          username: ${{ github.actor }}
-          password: ${{ secrets.GITHUB_TOKEN }}
 
       # This step uses [docker/metadata-action](https://github.com/docker/metadata-action#about) to extract tags and labels that will be applied to the specified image. The `id` "meta" allows the output of this step to be referenced in a subsequent step. The `images` value provides the base name for the tags and labels.
       - name: Extract metadata (tags, labels) for Docker
         id: meta
         uses: docker/metadata-action@8e5442c4ef9f78752691e2d8f8d19755c6f78e81
         with:
           images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
-          tags: |
-            type=ref,event=branch
-            type=semver,pattern={{version}}
-          flavor: |
-            ${{ env.FLAVOR_OPTS }}
 
       # This step uses the `docker/build-push-action` action to build the image, based on your repository's `Dockerfile`. If the build succeeds, it pushes the image to GitHub Packages.
       # It uses the `context` parameter to define the build's context as the set of files located in the specified path. For more information, see "[Usage](https://github.com/docker/build-push-action#usage)" in the README of the `docker/build-push-action` repository.
       # It uses the `tags` and `labels` parameters to tag and label the image with the output from the "meta" step.
       - name: Build and push Docker image
+        id: build
         uses: docker/build-push-action@f2a1d5e99d037542a71f64918e516c093c6f3fc4
         with:
+          platforms: ${{ matrix.platform }}
           context: .
           file: docker/${{ env.DOCKERFILE }}
-          push: true
-          tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
+          outputs: type=image,name=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }},push-by-digest=true,name-canonical=true,push=true
+
+      - name: Export digest
+        run: |
+          mkdir -p /tmp/digests
+          digest="${{ steps.build.outputs.digest }}"
+          touch "/tmp/digests/${digest#sha256:}"
+
+      - name: Upload digest
+        uses: actions/upload-artifact@v4
+        with:
+          name: digests-${{ matrix.base-image }}-${{ env.PLATFORM_PAIR }}
+          path: /tmp/digests/*
+          if-no-files-found: error
+          retention-days: 1
+
+  create-multi-arch-manifest:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    strategy:
+      fail-fast: false
+      matrix:
+        base-image: [debian, alpine]
+
+    needs:
+      - build-image
+    steps:
+      - name: Download digests
+        uses: actions/download-artifact@v4
+        with:
+          path: /tmp/digests
+          pattern: digests-${{ matrix.base-image }}-*
+          merge-multiple: true
+
+      - name: Prepare Docker image build
+        uses: ./.github/workflows/_prepare-image-build.yml
+        with:
+          registry: ${{ env.REGISTRY }}
+
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta
+        uses: docker/metadata-action@9ec57ed1fcdbf14dcef7dfbe97b2010124a938b7
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          tags: |
+            type=ref,event=branch
+            type=semver,pattern={{version}}
+          flavor: |
+            ${{ env.FLAVOR_OPTS }}
+
+      - name: Create multi-arch 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 }}/${{ env.IMAGE_NAME }}@sha256:%s ' *)