def directories_to_compact
      builds = Dir.entries builds_dir
      builds.select! {|e| File.directory? builds_dir(e) }
      builds.reject! {|e| %w{. ..}.include? e }
      builds.sort!
      
      builds = builds[0..-(@num_builds_to_leave+1)]
      builds.reject! {|e| @builds_to_leave.include?(e) || @builds_to_leave.include?(builds_dir(e, 'export'))}

      builds
    end
def directories_to_compact
      builds = Dir.entries builds_dir
      builds.select! {|e| File.directory? builds_dir(e) }
      builds.reject! {|e| %w{. ..}.include? e }
      builds.sort!
      
      builds = builds[0..-(@num_builds_to_leave+1)]
      builds.reject! {|e| @builds_to_leave.include?(e) || @builds_to_leave.include?(builds_dir(e, 'export'))}

      builds
    end
Build the list of directories to compact according to the options