ci: Add a flow that tests ostree container commit

To verify our changes there too.

.github/workflows/rust.yml

@@ -160,3 +160,21 @@ jobs:
         run: install ostree-ext-cli /usr/bin && rm -v ostree-ext-cli
       - name: Integration tests
         run: ./ci/priv-integration.sh
+  container-build:
+    name: "Container build"
+    needs: build
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+      - name: Checkout coreos-layering-examples
+        uses: actions/checkout@v3
+        with:
+          repository: coreos/coreos-layering-examples
+          path: coreos-layering-examples
+      - name: Download
+        uses: actions/download-artifact@v2
+        with:
+          name: ostree-ext-cli
+      - name: Integration tests
+        run: ./ci/container-build-integration.sh

ci/container-build-integration.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+# Verify `ostree container commit`
+set -euo pipefail
+
+image=quay.io/coreos-assembler/fcos:stable
+example=coreos-layering-examples/tailscale
+set -x
+
+mv ostree-ext-cli ${example}
+cd ${example}
+sed -ie 's,ostree container commit,ostree-ext-cli container commit,' Dockerfile
+sed -ie 's,^\(FROM .*\),\1\nADD ostree-ext-cli /usr/bin,' Dockerfile
+git diff
+
+docker build -t localhost/fcos-tailscale .
+
+docker run --rm -ti localhost/fcos-tailscale rpm -q tailscale
+
+echo ok container image integration