anchor.diff:      curl \
       git \
       git-man \
  -    imagemagick \
       keychain \
       nodejs \
       openssh-client \
       openssh-server \
  -    optipng \
       python-dev \
       python-pip \
       python-software-properties \
  
positive.code: 
  # Install Emacs 24.5 from source.
  
  RUN wget http://ftp.gnu.org/gnu/emacs/emacs-24.5.tar.gz
  RUN tar xzf emacs-24.5.tar.gz
  WORKDIR /tmp/build/emacs-24.5
  RUN ./configure && make && make install
  
  # Install Python 2.7.11.
  
  RUN apt-get update -y && apt-get install -y libffi-dev libffi6 libffi6-dbg
  RUN wget https://s3-us-west-1.amazonaws.com/royseto-public/dpkg/python2.7.11_2.7.11-local1_amd64.deb
  RUN dpkg -i python2.7.11_2.7.11-local1_amd64.deb
  
  # Enable passwordless sudo for users in the sudo group.
  
  
negative.code: 
  # Install RVM, Ruby, and gist.
  
  RUN gpg --keyserver hkp://keys.gnupg.net --recv-keys 409B6B1796C275462A1703113804BB82D39DC0E3 &&
      (curl -sSL https://get.rvm.io | bash -s stable --ruby) &&
      bash -c "(. /usr/local/rvm/scripts/rvm && gem install gist)"
  
  # Install npm packages.
  
  