anchor.diff:  # Default ENTRYPOINT
   ENV RACK_HANDLER webrick
   ENV RACK_ENV production
  -ENTRYPOINT bundle exec rackup -p $PORT /app/config.ru -s $RACK_HANDLER -E $RACK_ENV
  +ENTRYPOINT bundle exec rackup -p $PORT config.ru -s $RACK_HANDLER -E $RACK_ENV
  
positive.code: 
  # Preinstall ruby runtimes.
  # The LAST version in the list is set as the default.
  ENV PREINSTALLED_RUBY_VERSIONS 2.0.0-p647 2.1.7 2.2.3
  RUN for V in $PREINSTALLED_RUBY_VERSIONS; do \
      rbenv install $V; \
      rbenv rehash; \
  
negative.code: 
  # Install dependencies for Ruby
  # Also installs dependencies for the following common gems:
  #
  # gems      dependencies
  # ------------------------------------------------------------------
  # curb      libcurl3, libcurl3-gnutls, libcurl4-openssl-dev
  # pg        libpq-dev
  # rmagick   libmagickwand-dev
  # nokogiri  libxml2-dev, libxslt-dev
  # sqlite3   libsqlite3-dev
  # mysql2    libmysqlclient-dev
  
  