anchor.diff:  RUN apt-get install -y git
   
   # get a copy of the repository
  -RUN git clone https://github.com/nlesc-sherlock/punchcardjs-demo.git
  +RUN git clone https://github.com/nlesc-sherlock/punchcardjs-demo.git 
   
   # change into the directory
   WORKDIR /punchcardjs-demo
   
  -# Be explicit about which branch we're using
  -RUN git checkout master
  +# Be explicit about which commit we're using
  +RUN git checkout c6316a64f9f27a93e8fd76abee66c72f34737cb4
   
   # 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 this 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
  
negative.code: ## Removing the image goes like this:
  # docker rmi punchcardjs-image
  
  # 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
  