anchor.diff:  WORKDIR /usr/src/app
   
   # Define volumes.
  -VOLUME ["/home/rails", "/etc/rails", "/var/lib/rails", "/var/log/rails", "/tmp/rails"]
  +VOLUME ["${HOME}", "/etc/rails", "/var/lib/rails", "/var/log/rails", "/tmp/rails"]
   
   # Define the entrypoint
   ENTRYPOINT ["/docker-entrypoint"]
  
positive.code: # Copy the Gemfile into place and bundle.
  ONBUILD ADD Gemfile /usr/src/app/Gemfile
  ONBUILD ADD Gemfile.lock /usr/src/app/Gemfile.lock
  ONBUILD RUN echo "gem: --no-ri --no-rdoc" > ${HOME}/.gemrc
  ONBUILD RUN rm -rf .bundle && bundle install --retry 10 --without development test --deployment
  
  # Copy the rest of the application into place.
  ONBUILD ADD . /usr/src/app
  
negative.code:   dpkg -i wkhtmltox-*.deb && \
    rm -rf wkhtmltox-*
  
  # Define working directory.
  WORKDIR ${HOME}
  
  # Install ruby gems.
  RUN \
    echo "gem: --no-ri --no-rdoc" > ${HOME}/.gemrc && \
    gem install --no-ri --no-rdoc bundler
  
  # Clean up APT when done.
  RUN apt-get clean && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
  
  # Add files.
  COPY entrypoint.rb /docker-entrypoint
  