anchor.diff:  FROM  ubuntu:20.04
   
  +RUN echo 'force complete rebuild'
  +
   # install R
  -RUN apt update
  +RUN apt update 
  +RUN DEBIAN_FRONTEND=noninteractive apt dist-upgrade -y
   RUN apt install -y gnupg2 software-properties-common
   
   # RUN add-apt-repository deb https://cloud.r-project.org/bin/linux/ubuntu focal-cran40/
  
positive.code: # expose the RStudio IDE port
  EXPOSE 8787 
  
  # set the locale so RStudio doesn't complain about UTF-8
  RUN apt-get install  -y locales 
  RUN locale-gen en_US en_US.UTF-8
  RUN DEBIAN_FRONTEND=noninteractive dpkg-reconfigure locales
  
  CMD ["/usr/bin/supervisord"]
negative.code: RUN add-apt-repository 'deb https://cloud.r-project.org/bin/linux/ubuntu focal-cran40/'
  RUN apt update
  RUN DEBIAN_FRONTEND=noninteractive apt install -y r-base r-base-core r-recommended r-base-dev
  
  # we want OpenBLAS for faster linear algebra as described here: http://brettklamer.com/diversions/statistical/faster-blas-in-r/
  RUN apt-get install  -y \
  