Support building docker images for arm64 natively. (#1007)

* Try running arm builds on native platform and them combining them at the end.

* Rework flow for manifest making

* fix login action

* login to both

* Use a matrix loop

* try using json

* changelog

.github/workflows/docker.yml

@@ -22,28 +22,47 @@ concurrency:
 
 env:
   DOCKER_NAMESPACE: halfshot
-  PLATFORMS: linux/amd64
-  PLATFORMS_PUSH: linux/amd64,linux/arm64
-  # Only push if this is main, otherwise we just want to build
-  BUILD_FOR_ALL_PLATFORMS: ${{ github.ref == 'refs/heads/main' || github.event_name == 'release' }}
 
 jobs:
-  docker-latest:
+  docker-clean-metadata:
     runs-on: ubuntu-latest
+    outputs:
+      json: ${{ steps.meta.outputs.json }}
+    steps:
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          tags: |
+            type=semver,pattern={{version}}
+            type=ref,event=branch
+            type=ref,event=pr
+            type=raw,value=latest,enable={{is_default_branch}}
+          flavor: |
+            latest=auto
+          images: |
+            ${{ env.DOCKER_NAMESPACE }}/matrix-hookshot
+            ghcr.io/matrix-org/matrix-hookshot
 
+  docker-build:
     permissions:
       contents: read
       packages: write
       attestations: write
       id-token: write
+    strategy:
+      matrix:
+        include:
+          - os: ubuntu-latest
+            arch: amd64
+          - os: ubuntu-24.04-arm
+            arch: arm64
+
+    runs-on: ${{ matrix.os }}
 
     steps:
       - name: Checkout
         uses: actions/checkout@v4
-      - name: Set up QEMU
-        uses: docker/setup-qemu-action@v3
-      - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v3
       - name: Log in to Docker Hub
         uses: docker/login-action@v3
         with:
@@ -55,7 +74,6 @@ jobs:
           registry: ghcr.io
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
-
       - name: Extract metadata (tags, labels) for Docker
         id: meta
         uses: docker/metadata-action@v5
@@ -65,20 +83,45 @@ jobs:
             type=ref,event=branch
             type=ref,event=pr
             type=raw,value=latest,enable={{is_default_branch}}
+          flavor: |
+            latest=auto
+            suffix=-${{ matrix.arch }},onlatest=true
           images: |
             ${{ env.DOCKER_NAMESPACE }}/matrix-hookshot
             ghcr.io/matrix-org/matrix-hookshot
 
       - name: Build and push Docker images
-        id: push
         uses: docker/build-push-action@v6
         with:
-          context: .
-          # arm64 builds OOM without the git fetch setting. c.f.
-          # https://github.com/rust-lang/cargo/issues/10583
-          build-args: |
-            CARGO_NET_GIT_FETCH_WITH_CLI=true
-          platforms: ${{ (env.BUILD_FOR_ALL_PLATFORMS == 'true' && env.PLATFORMS_PUSH) || env.PLATFORMS }}
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
+
+  docker-manifest:
+    needs: 
+      - docker-build
+      - docker-clean-metadata
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        image: ${{ fromJson(needs.docker-clean-metadata.outputs.json).tags }}
+
+    steps:
+      - name: Log in to Docker Hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKER_HUB_USERNAME }}
+          password: ${{ secrets.DOCKER_HUB_TOKEN }}
+
+      - name: Log in to the GitHub Container registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Create and push manifest
+        run: |
+          docker manifest create ${{ matrix.image }} ${{ matrix.image }}-amd64 ${{ matrix.image }}-arm64
+          docker manifest push ${{ matrix.image }}

changelog.d/1008.misc

@@ -0,0 +1 @@
+Switch to using GitHub Actions native arm runners for Docker builds, which will reduce build times.