use multiple runners for the multi-arch build

.gitea/workflows/ci.yml

@@ -85,7 +85,7 @@ jobs:
         uses: docker/metadata-action@v5
         with:
           images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
-      - name: Login to the Container Registry
+      - name: Login to the container registry
         uses: docker/login-action@v3
         with:
           registry: brosner.dev
@@ -109,9 +109,45 @@ jobs:
           digest="${{ steps.build.outputs.digest }}"
           touch "${{ runner.temp }}/digests/${digest#sha256:}"
       - name: Upload digest
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: digests-${{ env.PLATFORM_PAIR }}
           path: ${{ runner.temp }}/digests/*
           if-no-files-found: error
           retention-days: 1
+  merge:
+    runs-on: ubuntu-latest
+    needs:
+      - build
+    steps:
+      - name: Download digests
+        uses: actions/download-artifact@v4
+        with:
+          path: ${{ runner.temp }}/digests
+          pattern: digests-*
+          merge-multiple: true
+      - name: Login to the container registry
+        uses: docker/login-action@v3
+        with:
+          registry: brosner.dev
+          username: brosner
+          password: ${{ secrets.CI_TOKEN }}
+      - name: Setup docker buildx
+        uses: docker/setup-buildx-action@v3
+      - name: Generate metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          tags: |
+            type=ref,event=branch
+            type=ref,event=pr
+            type=sha
+      - name: Create manifest list and push
+        working-directory: ${{ runner.temp }}/digests
+        run: |
+          docker buildx imagetools create $(jq -cr '.tags | map("-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
+            $(printf '${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}@sha256:%s ' *)
+      - name: Inspect image
+        run: |
+          docker buildx imagetools inspect ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ steps.meta.outputs.version }}