anchor.diff:  # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   # 1. install ruby
   # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  +
   RUN apk --update --no-cache add \
       openssl ca-certificates \
       ruby ruby-io-console ruby-dev ruby-irb ruby-bundler ruby-bigdecimal \
       bash tzdata
  -
  -RUN adduser -D -H -u 19661 cyber-dojo
   
   # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   # 2. install tini (for pid 1 zombie reaping)
  
positive.code: #    docker-and-the-pid-1-zombie-reaping-problem/
  
  RUN apk add --update --repository http://dl-cdn.alpinelinux.org/alpine/edge/community/ tini
  ENTRYPOINT ["/sbin/tini", "--"]
  
  # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  # 3. install sinatra
  
negative.code: 
  # tarpipe: Default Alpine tar does not support --owner/--group options
  RUN apk --update add tar
  COPY . /app
  ARG PORT
  EXPOSE ${PORT}
  ENV PORT=${PORT}
  
  ENTRYPOINT ["/sbin/tini", "--"]
  CMD [ "./up.sh" ]
  
  