anchor.diff:  
   # Environments
   ENV RAILS_ENV=${RAILS_ENV}
  +ENV RAILS_ROOT=/var/www/app
  +
   # Image metadata
   LABEL org.dmptool.git.remote=$GIT \
         org.dmptool.git.release=$RELEASE \
  
positive.code: # I don't know why, but gems are installed with disregard towards our directory
  # permissions. So we do the stuff from above again and remove it when the issue
  # is fixed.
  RUN chgrp -R www-data    /var/www/app/vendor/bundle \
      && chmod -R g+s,g-w  /var/www/app/vendor/bundle
  
  # Copy static/initial configuration
  COPY dist/etc /etc/
  
negative.code:         zlib1g-dev
  
  # Have root own the application directory, but enable www-data group everywhere
  RUN mkdir -p          ${RAILS_ROOT} /var/www/.bundler \
      && chgrp www-data ${RAILS_ROOT} /var/www/.bundler \
      && chmod g+s,g-w  ${RAILS_ROOT} /var/www/.bundler
  
  # Setup the web app's codebase
  RUN git clone --branch $RELEASE --single-branch --depth 1 $GIT ${RAILS_ROOT} \
  #
  # www-data should be able to do everything with the tmp directory
      && mkdir ${RAILS_ROOT}/tmp \
      && chown www-data ${RAILS_ROOT}/tmp
  
  # Install app dependencies
  RUN cd ${RAILS_ROOT} \
      # tidy-ext doesn't compile with Debian's default MRI cflags.
      && bundle config build.tidy-ext --with-cflags="-O2 -pipe -march=native" \
      # Really install dependencies
  