ci: build container

Automatically build the container for `image-builder-cli` and upload it
to `ghcr.io`. This builds only for x86 initially.

Signed-off-by: Simon de Vlieger <supakeen@redhat.com>

.github/workflows/container.yaml

@@ -0,0 +1,48 @@
+name: Build & Deploy Container
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+  merge_group:
+    types: [ "checks_requested" ]
+
+jobs:
+  build-base:
+    name: Build & push image
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+
+      - name: Login to Github Container Registry
+        uses: docker/login-action@v2
+        with:
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Generate container image metadata
+        uses: docker/metadata-action@v4
+        id: meta
+        with:
+          images: ghcr.io/osbuild/image-builder-cli
+          tags: |
+            type=ref,event=tag,enable=${{ startsWith(github.ref, 'refs/tags/') }}
+            type=raw,value=latest
+            type=sha,format=long,enable=${{ github.ref == 'refs/heads/main' }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v4
+        with:
+          context: .
+          platforms: linux/amd64
+          file: ./Containerfile
+          push: ${{ github.ref == 'refs/heads/main' || startsWith(github.ref, 'refs/tags/') }}
+          cache-from: type=registry,ref=ghcr.io/osbuild/image-builder-cli:latest
+          cache-to: type=inline
+          tags: ${{ steps.meta.outputs.tags }}