ci: run arm64 at night only; cache builds; push amd64 on push; nightly creates multi-arch manifest

Author: dvershinin

.github/workflows/main.yml

@@ -79,10 +79,10 @@ jobs:
           password: ${{ secrets.DOCKERHUB_TOKEN }}
 
       - name: Set up QEMU
-        if: inputs.push == true || github.event_name == 'push' || github.event_name == 'schedule'
+        if: github.event_name == 'schedule'
         uses: docker/setup-qemu-action@v3
         with:
-          platforms: linux/amd64,linux/arm64
+          platforms: linux/arm64
 
       - name: Set up Docker Buildx
         if: inputs.push == true || github.event_name == 'push' || github.event_name == 'schedule'
@@ -124,13 +124,37 @@ jobs:
           docker run --rm --network host curl-edge:${IMAGE_TAG} \
             /opt/httpstat.sh -I --http3 https://cloudflare-quic.com/ || true
 
-      - name: Build and push
-        if: inputs.push == true || github.event_name == 'push' || github.event_name == 'schedule'
+      - name: Build and push (push/dispatch, amd64 only)
+        if: inputs.push == true || github.event_name == 'push'
         uses: docker/build-push-action@v4
         with:
           context: .
           push: true
-          platforms: linux/amd64,linux/arm64
+          platforms: linux/amd64
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
           tags: |
-            getpagespeed/curl-edge:${{ env.IMAGE_TAG }}
-            getpagespeed/curl-edge:latest
+            getpagespeed/curl-edge:amd64-${{ env.IMAGE_TAG }}
+            getpagespeed/curl-edge:latest-amd64
+
+      - name: Build and push (nightly, arm64 only)
+        if: github.event_name == 'schedule'
+        uses: docker/build-push-action@v4
+        with:
+          context: .
+          push: true
+          platforms: linux/arm64
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+          tags: |
+            getpagespeed/curl-edge:arm64-${{ env.IMAGE_TAG }}
+            getpagespeed/curl-edge:latest-arm64
+
+      - name: Create multi-arch manifest (nightly)
+        if: github.event_name == 'schedule'
+        run: |
+          docker buildx imagetools create \
+            -t getpagespeed/curl-edge:${IMAGE_TAG} \
+            -t getpagespeed/curl-edge:latest \
+            getpagespeed/curl-edge:amd64-${IMAGE_TAG} \
+            getpagespeed/curl-edge:arm64-${IMAGE_TAG}