Add CI to check that we can build the production site

.github/workflows/pr-build.yml

@@ -0,0 +1,41 @@
+name: Test PR
+
+on:
+  pull_request:
+    types: [ opened, synchronize, reopened ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    services:
+      registry:
+        image: registry:2
+        ports:
+          - 5000:5000
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+        with:
+          # this is required for the subsequent build to be able to push to the registry on localhost:5000
+          driver-opts: network=host
+
+      - name: Build Docker image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          push: true
+          tags: localhost:5000/kroxy-jekyll:latest
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+
+      - name: Build with Jekyll
+        run: |
+          docker run \
+            --rm \
+            -u "$(id -u):$(id -g)" \
+            -v "$(pwd):/site" \
+            localhost:5000/kroxy-jekyll:latest \
+            bash -c 'eval "$(rbenv init -)" && cp -r /css/_sass/bootstrap /site/_sass/ && JEKYLL_ENV=production bundle exec jekyll build --config=_config.yml'

Dockerfile

@@ -17,7 +17,7 @@ RUN apt-get update && \
                    wget \
                    golang && \
                    rm -rf /var/lib/apt/lists/*
-ENV RBENV_ROOT /usr/local/rbenv
+ENV RBENV_ROOT=/usr/local/rbenv
 RUN git clone https://github.com/rbenv/rbenv.git ${RBENV_ROOT} && \
     git clone https://github.com/rbenv/ruby-build.git ${RBENV_ROOT}/plugins/ruby-build
 
@@ -45,4 +45,4 @@ RUN mkdir /site/
 WORKDIR /site/
 EXPOSE 4000
 # Note --incremental mode is ineffective on the Mac owing to https://github.com/containers/podman/issues/22343.  Use force_regenerate.sh to trigger the incremental reload after changing the file on the host.
-CMD eval "$(rbenv init -)" && cp -r /css/_sass/bootstrap /site/_sass/ && bundle exec jekyll serve --host ${JEKYLL_SERVE_BIND} --incremental --disable-disk-cache --destination /tmp/site
+CMD [ "bash", "-c", "eval \"$(rbenv init -)\" && cp -r /css/_sass/bootstrap /site/_sass/ && bundle exec jekyll serve --host ${JEKYLL_SERVE_BIND} --incremental --disable-disk-cache --destination /tmp/site"]