anchor.diff:  
   RUN mkdir -p /dungeon_assets/
   RUN mkdir -p /dungeon/
  -COPY Gemfile /dungeon/
  -COPY Gemfile.lock /dungeon/
  -RUN cd /dungeon && bundle install
  +WORKDIR /dungeon
  +COPY Gemfile Gemfile.lock ./
  +RUN bundle install
  +
  +COPY package.json yarn.lock ./
  +RUN yarn install --production=true
   
   COPY . /dungeon
  -WORKDIR /dungeon
   ENV RAILS_ENV docker
   
   RUN chmod a+x /dungeon/docker/web_boot.sh
  
positive.code:     libvips-dev \
      libvips-tools \
      nodejs \
      && apt-get clean \
      && rm -rf /var/lib/apt/lists/*
  
  
negative.code: FROM ruby:2.5.1-stretch
  
  RUN curl -sL https://deb.nodesource.com/setup_8.x | bash - && \
      curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add - && \
      echo "deb https://dl.yarnpkg.com/debian/ stable main" > /etc/apt/sources.list.d/yarn.list && \
      apt-get update && apt-get install -y \
      rsync \
      cmake \
  