Add initial GitHub Actions

.github/workflows/ci.yml

@@ -0,0 +1,29 @@
+name: GitHub CI
+
+on:
+  pull_request:
+  push:
+  schedule:
+    - cron: 0 0 * * 0
+
+defaults:
+  run:
+    shell: 'bash -Eeuo pipefail -x {0}'
+
+jobs:
+  build:
+    name: Build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - name: Build
+        run: |
+          docker build --tag bashbrew --pull .
+          docker run --rm bashbrew tar -cC /usr/local/bin bashbrew | tar -xv
+          ./bashbrew --help > /dev/null
+      - name: Smoke Test
+        run: |
+          image='https://github.com/docker-library/official-images/raw/master/library/hello-world'
+          ./bashbrew list "$image"
+          ./bashbrew list --uniq "$image"
+          ./bashbrew cat "$image"