Reduce size of container image (#1777)

* Reduce size of container image
* Add deprecation message for automatic --mathjax

.github/workflows/docker-test.yml

@@ -34,5 +34,5 @@ jobs:
         run: echo ${{ steps.docker_build.outputs.digest }}
       - name: docker state
         run: docker image ls
-      - name: Run tests
-        run: docker run -e CI=true -w /app --entrypoint bundle ${{ env.CI_IMAGE }} exec rake
+      - name: Run gollum as test
+        run: docker run -e CI=true ${{ env.CI_IMAGE }} --irb

Dockerfile

@@ -1,9 +1,11 @@
-FROM ruby:2.7
-ENV DEBIAN_FRONTEND="noninteractive"
+FROM ruby:2.7-alpine AS builder
 
-RUN apt-get update && apt-get install -y \
-    libicu-dev \
-    cmake
+RUN apk add \
+    build-base \
+    cmake \
+    git \
+    icu-dev \
+    openssl-dev
 
 COPY Gemfile* /tmp/
 COPY gollum.gemspec* /tmp/
@@ -23,6 +25,15 @@ WORKDIR /app
 COPY . /app
 RUN bundle exec rake install
 
+
+FROM ruby:2.7-alpine
+
+COPY --from=builder /usr/local/bundle/ /usr/local/bundle/
+
+RUN apk add \
+    bash \
+    git
+
 VOLUME /wiki
 WORKDIR /wiki
 COPY docker-run.sh /docker-run.sh

docker-run.sh

@@ -6,4 +6,5 @@ if [ ! -d .git ]; then
 fi
 
 # Start gollum service
-gollum --mathjax
+[[ "$@" != *--mathjax* ]] && echo "WARNING: Mathjax will soon be disabled by default. To explicitly enable it, use --mathjax" >&2
+exec gollum $@ --mathjax