anchor.diff:  # docker images
   ##
   ## Removing the image goes like this:
  -# docker rmi punchcardjs-image
  +# docker rmi image-punchcardjs-demo
   
   # start from Node's offical docker image, version 7.0 (https://hub.docker.com/r/library/node/)
   FROM node:7.0
   
   # open network port (at outside of the container)
  -EXPOSE 5000
  +EXPOSE 80
   
   # do the updates
   RUN apt-get update
   
  -# install version management git
  -RUN apt-get install -y git
  +# install python3
  +RUN apt-get install -y python3
   
  -# get a copy of the repository
  -RUN git clone https://github.com/nlesc-sherlock/punchcardjs-demo.git 
  +# prepare a directory to copy the repository to
  +RUN mkdir /punchcardjs-demo
   
  -# change into the directory
  +# add files from the docker context to the directory we just prepared
  +ADD . /punchcardjs-demo/
  +
  +# set the work directory using absolute paths
   WORKDIR /punchcardjs-demo
  -
  -# Be explicit about which commit we're using
  -RUN git checkout 12dee71297710e8cf40b43ce54194b7909402387
   
   # install the dependencies listed in package.json
   RUN npm install
  
positive.code: ## First install docker on your machine
  ## Then you can build the docker image with this command (the build looks
  ## in the current file):
  # docker build -t image-punchcardjs-demo .
  ## Then run the docker container using this command:
  # docker run -p 5001:5000 --name prosperous-punchcards image-punchcardjs-demo
  ##
  ## Now you should be able to open a browser (on the host) and navigate to
  ## http://localhost:5001 and see the webapp being served.
  ##
  ## When you're done, run
  # docker stop prosperous-punchcards
  
negative.code: # fill the sites/demo/ directory with the demo website's content
  RUN npm run demo
  
  # change into the demo directory
  WORKDIR /punchcardjs-demo/docs/sites/demo
  
  # define the container's task: serving the app
  CMD python3 -m http.server 80
  