ci: build release Docker images natively per-arch, merge with a manifest

The v0.6.0 release run's multi-arch Docker build wedged for 3+ hours
emulating the arm64 Rust release build under QEMU, and — because the
workflow concurrency group is cancel-in-progress:false — every queued
release run sat blocked behind it.

- docker is now a matrix: amd64 on ubuntu-latest, arm64 on
  ubuntu-24.04-arm — both native, mirroring release-binaries. Each leg
  smoke-tests the image (--version must report the released version)
  and pushes by digest only.
- docker-manifest stitches the digests into the :X.Y.Z, :X.Y and
  :latest tags with buildx imagetools, so a half-finished matrix can
  never publish a partially-tagged image.
- workflow_dispatch grows docker_backfill_tag (and npm_backfill_tag
  becomes optional): each channel backfills independently for an
  already-cut release — needed to publish the missing v0.6.0 image.

Author: kevincodex1

.github/workflows/release.yml

@@ -4,15 +4,19 @@ on:
   push:
     branches:
       - main
-  # Manual backfill: publish an already-cut release to npm (e.g. after the
-  # npm side of trusted publishing is configured, or a publish was missed).
-  # Only the npm-publish job runs; binaries are downloaded from the existing
-  # GitHub release for the given tag.
+  # Manual backfill: republish an already-cut release to a channel that
+  # missed it. Fill in only the channel(s) you want — an empty input leaves
+  # that channel's jobs skipped. npm reuses the existing release's binary
+  # assets; docker rebuilds the image from the tag and re-tags the manifest.
   workflow_dispatch:
     inputs:
       npm_backfill_tag:
         description: "Existing release tag to publish to npm (e.g. v0.6.0)"
-        required: true
+        required: false
+        type: string
+      docker_backfill_tag:
+        description: "Existing release tag to publish to ghcr (e.g. v0.6.0)"
+        required: false
         type: string
 
 concurrency:
@@ -44,24 +48,57 @@ jobs:
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
 
+  # Each architecture builds NATIVELY (amd64 on ubuntu-latest, arm64 on
+  # ubuntu-24.04-arm) and pushes by digest; docker-manifest below stitches the
+  # digests into the tagged multi-arch image. No QEMU: emulating the arm64
+  # Rust release build wedged the v0.6.0 run for 3+ hours and, via the
+  # workflow concurrency group, blocked every queued release run behind it.
   docker:
-    name: Build & Push Docker Image
+    name: Build & Push Docker Image (${{ matrix.arch }})
     needs: release-please
-    if: ${{ needs.release-please.outputs.release_created == 'true' }}
-    runs-on: ubuntu-latest
+    # Runs on a fresh release, or on manual dispatch for an existing tag
+    # (release-please is skipped on dispatch, hence !cancelled()).
+    if: >-
+      ${{ !cancelled() && (
+        needs.release-please.outputs.release_created == 'true' ||
+        (github.event_name == 'workflow_dispatch' && inputs.docker_backfill_tag != '')
+      ) }}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - arch: amd64
+            os: ubuntu-latest
+            platform: linux/amd64
+          - arch: arm64
+            os: ubuntu-24.04-arm
+            platform: linux/arm64
+    runs-on: ${{ matrix.os }}
     permissions:
       contents: read
       packages: write
     steps:
+      - name: Resolve release tag
+        id: rel
+        env:
+          DISPATCH_TAG: ${{ inputs.docker_backfill_tag }}
+          RELEASE_TAG: ${{ needs.release-please.outputs.tag_name }}
+        run: |
+          set -euo pipefail
+          TAG="${DISPATCH_TAG:-$RELEASE_TAG}"
+          case "$TAG" in
+            v[0-9]*) ;;
+            *) echo "::error::'$TAG' does not look like a release tag (vX.Y.Z)"; exit 1 ;;
+          esac
+          echo "tag=$TAG" >> "$GITHUB_OUTPUT"
+          echo "version=${TAG#v}" >> "$GITHUB_OUTPUT"
+
       - name: Checkout release tag
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
-          ref: ${{ needs.release-please.outputs.tag_name }}
+          ref: ${{ steps.rel.outputs.tag }}
           persist-credentials: false
 
-      - name: Set up QEMU
-        uses: docker/setup-qemu-action@29109295f81e9208d7d86ff1c6c12d2833863392 # v3.6.0
-
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@b5ca514318bd6ebac0fb2aedd5d36ec1b5c232a2 # v3.10.0
 
@@ -72,45 +109,130 @@ jobs:
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
-      - name: Extract metadata
-        id: meta
-        uses: docker/metadata-action@902fa8ec7d6ecbf8d84d538b9b233a880e428804 # v5.7.0
-        with:
-          images: ghcr.io/${{ github.repository }}
-          tags: |
-            type=semver,pattern={{version}},value=${{ needs.release-please.outputs.version }}
-            type=semver,pattern={{major}}.{{minor}},value=${{ needs.release-please.outputs.version }}
-            type=raw,value=latest
-
       - name: Build and load locally (smoke)
         uses: docker/build-push-action@14487ce63c7a62a4a324b0bfb37086795e31c6c1 # v6.16.0
         with:
           context: .
+          platforms: ${{ matrix.platform }}
           load: true
           tags: gitlawb-node:smoke
-          cache-from: type=gha
+          cache-from: type=gha,scope=docker-${{ matrix.arch }}
 
+      # Native runner on both arches, so the built image can always execute.
+      # Assert the released version so a stale artifact fails here, not in prod.
       - name: Smoke test
-        run: docker run --rm gitlawb-node:smoke --version
+        env:
+          VERSION: ${{ steps.rel.outputs.version }}
+        run: |
+          set -euo pipefail
+          out="$(docker run --rm gitlawb-node:smoke --version)"
+          echo "$out"
+          grep -qF "$VERSION" <<<"$out" || {
+            echo "::error::image --version did not report expected version $VERSION (got: $out)"
+            exit 1
+          }
 
-      - name: Build and push (multi-arch)
+      # Push by digest only — tags are applied once by docker-manifest so a
+      # half-finished matrix can never publish a partially-tagged image.
+      # provenance:false keeps each push a plain single-arch manifest, which is
+      # what imagetools create expects to merge.
+      - name: Build and push by digest
+        id: push
         uses: docker/build-push-action@14487ce63c7a62a4a324b0bfb37086795e31c6c1 # v6.16.0
         with:
           context: .
-          platforms: linux/amd64,linux/arm64
-          push: true
-          tags: ${{ steps.meta.outputs.tags }}
-          labels: ${{ steps.meta.outputs.labels }}
-          cache-from: type=gha
-          cache-to: type=gha,mode=max
+          platforms: ${{ matrix.platform }}
+          provenance: false
+          outputs: type=image,name=ghcr.io/${{ github.repository }},push-by-digest=true,name-canonical=true,push=true
+          cache-from: type=gha,scope=docker-${{ matrix.arch }}
+          cache-to: type=gha,mode=max,scope=docker-${{ matrix.arch }}
+
+      - name: Export digest
+        env:
+          DIGEST: ${{ steps.push.outputs.digest }}
+        run: |
+          set -euo pipefail
+          mkdir -p /tmp/digests
+          touch "/tmp/digests/${DIGEST#sha256:}"
+
+      - name: Upload digest
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4.6.2
+        with:
+          name: docker-digest-${{ matrix.arch }}
+          path: /tmp/digests/*
+          if-no-files-found: error
+          retention-days: 1
+
+  docker-manifest:
+    name: Publish Docker manifest
+    needs: [release-please, docker]
+    if: ${{ !cancelled() && needs.docker.result == 'success' }}
+    runs-on: ubuntu-latest
+    permissions:
+      packages: write
+    steps:
+      - name: Resolve release tag
+        id: rel
+        env:
+          DISPATCH_TAG: ${{ inputs.docker_backfill_tag }}
+          RELEASE_TAG: ${{ needs.release-please.outputs.tag_name }}
+        run: |
+          set -euo pipefail
+          TAG="${DISPATCH_TAG:-$RELEASE_TAG}"
+          case "$TAG" in
+            v[0-9]*) ;;
+            *) echo "::error::'$TAG' does not look like a release tag (vX.Y.Z)"; exit 1 ;;
+          esac
+          echo "tag=$TAG" >> "$GITHUB_OUTPUT"
+          echo "version=${TAG#v}" >> "$GITHUB_OUTPUT"
+
+      - name: Download digests
+        uses: actions/download-artifact@d3f86a106a0bac45b974a628896c90dbdf5c8093 # v4.3.0
+        with:
+          pattern: docker-digest-*
+          path: /tmp/digests
+          merge-multiple: true
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@b5ca514318bd6ebac0fb2aedd5d36ec1b5c232a2 # v3.10.0
+
+      - name: Log in to GitHub Container Registry
+        uses: docker/login-action@74a5d142397b4f367a81961eba4e8cd7edddf772 # v3.4.0
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Create and push multi-arch manifest
+        env:
+          VERSION: ${{ steps.rel.outputs.version }}
+        run: |
+          set -euo pipefail
+          # ghcr requires a lowercase repository path.
+          IMAGE="ghcr.io/${GITHUB_REPOSITORY,,}"
+          MAJOR_MINOR="${VERSION%.*}"
+          digests=""
+          for f in /tmp/digests/*; do
+            digests="$digests $IMAGE@sha256:$(basename "$f")"
+          done
+          # shellcheck disable=SC2086
+          docker buildx imagetools create \
+            -t "$IMAGE:$VERSION" \
+            -t "$IMAGE:$MAJOR_MINOR" \
+            -t "$IMAGE:latest" \
+            $digests
+          docker buildx imagetools inspect "$IMAGE:$VERSION"
 
       - name: Release summary
+        env:
+          VERSION: ${{ steps.rel.outputs.version }}
+          TAG: ${{ steps.rel.outputs.tag }}
         run: |
           {
-            echo "## Released ${{ needs.release-please.outputs.tag_name }}"
+            echo "## Released $TAG"
             echo
-            echo "- Image: \`ghcr.io/${{ github.repository }}:${{ needs.release-please.outputs.version }}\`"
-            echo "- GitHub: https://github.com/${{ github.repository }}/releases/tag/${{ needs.release-please.outputs.tag_name }}"
+            echo "- Image: \`ghcr.io/${GITHUB_REPOSITORY,,}:$VERSION\` (linux/amd64 + linux/arm64)"
+            echo "- GitHub: https://github.com/$GITHUB_REPOSITORY/releases/tag/$TAG"
           } >> "$GITHUB_STEP_SUMMARY"
 
   release-binaries: