anchor.diff:  ENV DEBIAN_FRONTEND noninteractive
   
   # increment version to force flushing the cache
  -RUN echo "Version 1.3"
  +RUN echo "Version 1.4"
   
   RUN echo "enable universe packages" && \
       sed -r 's/#\s*(.*universe)$/\1/' -i /etc/apt/sources.list && \
  
positive.code: RUN apt-get install -y openjdk-7-doc openjdk-7-jdk
  RUN apt-get install -y ant maven2
  
  # editors
  RUN apt-get install -y vim vim-addon-manager vim-vimoutliner vim-doc 
  RUN apt-get install -y emacs ctags indent
  
negative.code: # GO
  RUN curl https://go.googlecode.com/files/go1.2.1.linux-amd64.tar.gz | tar -C /usr/local -xzf -
  
  # all changes go down here:
  # RUN ...
  
  