anchor.diff:    tar \
     tree \
     which \
  -  zlib-devel 
  -  
  +  zlib-devel
   
   ## add rbenv group
   RUN groupadd rbenv
  
positive.code:   libxslt-devel \
    libyaml-devel \
    make \
    openssh \
    openssh-clients \
    openssh-server \
  
negative.code: FROM centos:centos6
  MAINTAINER pepechoko
  
  RUN 
    yum update -y && \
    apt-get clean && \
    rm -rf /var/cache/apt/archives/* /var/lib/apt/lists/* 
  
  RUN \
    rpm -Uvh http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm
  
  RUN yum install -y --no-install-recommends \
    autoconf \
    automake \
    curl-devel \
  