anchor.diff:  
   def root
     status, stdout, stderr = rbenv_command("root")
  +  status == 0 ? stdout : nil
  +end
  +
  +def version
  +  status, stdout, stderr = rbenv_command("version-name")
     status == 0 ? stdout : nil
   end
   
  
positive.code:   versions
  end
  
  rbenv[:root]     = root
  rbenv[:prefix]   = prefix
  rbenv[:global]   = global
  rbenv[:versions] = versions
  
negative.code: 
  provides "rbenv"
  provides "rbenv/root"
  provides "rbenv/current_version"
  provides "rbenv/current_version_prefix"
  provides "rbenv/global"
  provides "rbenv/versions"
  
  