anchor.diff:  
   # Base image for all Discourse related processes.
   
  +# NOTE to dev: do not have too many RUN commands; see
  +# https://github.com/dotcloud/docker/issues/1171
  +
  +
   FROM ubuntu:12.04
   MAINTAINER srid
   
  -RUN apt-get -qy update
  +ENV DISCOURSE_VERSION 0.9.6.2
   
  -RUN apt-get -qy install git 
  +RUN apt-get -qy update && apt-get -qy install git 
   
   # Get discourse stable tag
  -RUN git clone --depth 1 https://github.com/discourse/discourse.git
  -RUN cd discourse && git checkout v0.9.6.1
  +RUN git clone --depth 1 https://github.com/discourse/discourse.git && cd discourse && git checkout v$DISCOURSE_VERSION
   
   # We don't care about having .git on an ephemeral filesystem.
   RUN rm -rf .git
  
positive.code: # https://github.com/discourse/discourse/blob/master/docs/INSTALL-ubuntu.md
  #
  
  RUN echo "deb http://archive.ubuntu.com/ubuntu precise main universe" > /etc/apt/sources.list
  RUN apt-get -qy update
  RUN apt-get -qy install build-essential libssl-dev libyaml-dev git libtool libxslt-dev libxml2-dev libpq-dev gawk curl pngcrush python-software-properties
  
  # nginx
  # TODO: move to different container?
  RUN apt-get remove '^nginx.*$'
  
  RUN echo "deb http://nginx.org/packages/ubuntu/ precise nginx" >> /etc/apt/sources.list
  RUN echo "deb-src http://nginx.org/packages/ubuntu/ precise nginx" >> /etc/apt/sources.list
  RUN curl http://nginx.org/keys/nginx_signing.key | apt-key add -
  
  RUN apt-get -qy update
  RUN apt-get -qy install nginx
  
  
  # Discourse setup
  #
  
negative.code: # RUN su - postgres -c "createuser -s discourse"
  
  # Install Ruby 2.0.0 (not bothering to use RVM)
  RUN add-apt-repository ppa:brightbox/ruby-ng-experimental  && apt-get -qy update
  RUN apt-get -qy install ruby2.0 ruby2.0-dev
  
  RUN echo "gem: --no-ri --no-rdoc" > ~/.gemrc
  