CI: Add multi-platform image build

Signed-off-by: Knut Ahlers <knut@ahlers.me>

.github/workflows/docker-publish.yml

@@ -18,6 +18,12 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
       - uses: actions/checkout@v4
         with:
           lfs: true
@@ -31,6 +37,15 @@ jobs:
           password: ${{ secrets.GITHUB_TOKEN }}
 
       - name: Docker Build & Publish
-        run: bash ci/docker-publish.sh
+        id: taggen
+        run: bash ci/docker-gen-tagnames.sh
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          platforms: linux/amd64,linux/arm64
+          push: true
+          tags: ${{ steps.taggen.outputs.docker_build_tags }}
 
 ...

ci/docker-gen-tagnames.sh

@@ -5,7 +5,7 @@ function log() {
   echo "[$(date +%H:%M:%S)] $@" >&2
 }
 
-[[ -n $GITHUB_REF_NAME ]] || {
+[[ -n ${GITHUB_REF_NAME:-} ]] || {
   log "ERR: This script is intended to run on a Github Action only."
   exit 1
 }
@@ -16,11 +16,11 @@ tags=()
 case "${GITHUB_REF_TYPE}" in
 branch)
   # Generic build to develop: Workflow has to limit branches to master
-  tags+=(develop)
+  tags+=("${repo}:develop")
   ;;
 tag)
   # Build to latest & tag: Older tags are not intended to rebuild
-  tags+=(latest ${GITHUB_REF_NAME})
+  tags+=("${repo}:latest" "${repo}:${GITHUB_REF_NAME}")
   ;;
 *)
   log "ERR: The ref type ${GITHUB_REF_TYPE} is not handled."
@@ -28,13 +28,5 @@ tag)
   ;;
 esac
 
-log "Building Docker image..."
-docker build -t "${repo}:local" .
-
-for ref in "${tags[@]}"; do
-  log "Pushing Docker image to '${repo}:${ref}'..."
-  docker tag "${repo}:local" "${repo}:${ref}"
-  docker push "${repo}:${ref}"
-done
-
-log "Publish finished."
+export IFS=,
+echo "docker_build_tags=${tags[*]}" >>${GITHUB_OUTPUT}