Add GH action to build/push docker image

.github/workflows/docker-build-push.yml

@@ -0,0 +1,63 @@
+name: Docker
+
+on:
+  push:
+    branches:
+      - master
+      - upgrade-os
+    tags:
+      - v*
+
+env:
+  IMAGE_NAME: hammady/scaltainer
+
+jobs:
+  docker:
+    runs-on: ubuntu-latest
+    if: github.event_name == 'push'
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Determine target image name
+        id: image-name
+        run: |
+          IMAGE_ID=ghcr.io/$IMAGE_NAME
+
+          # Strip git ref prefix from version
+          VERSION=$(echo "${{ github.ref }}" | sed -e 's,.*/\(.*\),\1,')
+
+          # Strip "v" prefix from tag name
+          [[ "${{ github.ref }}" == "refs/tags/"* ]] && VERSION=$(echo $VERSION | sed -e 's/^v//')
+
+          # Use Docker `latest` tag convention
+          [ "$VERSION" == "master" ] && VERSION=latest
+
+          IMAGES=
+          IMAGES="$IMAGE_ID:$VERSION"$'\n'$IMAGES
+
+          # debug output
+          echo images $IMAGES
+          echo ::set-output name=images::"$IMAGES"
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+
+      - name: Login to registry
+        uses: docker/login-action@v1
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v2
+        with:
+          context: .
+          platforms: linux/amd64,linux/arm64,linux/arm/v7
+          push: true
+          tags: ${{ steps.image-name.outputs.images }}