def master_for( key )
      return if @masters.empty?
      key = to_key(key)

      loop do
        break key if @masters.include? key
        break nil if :root == key

        if index = key.rindex(PATH_DELIMITER)
          key = key.slice(0, index)
        else
          key = :root
        end
      end
    end
def master_for( key )
      return if @masters.empty?
      key = to_key(key)

      loop do
        break key if @masters.include? key
        break nil if :root == key

        if index = key.rindex(PATH_DELIMITER)
          key = key.slice(0, index)
        else
          key = :root
        end
      end
    end
call-seq:
    master_for( key )

 Returns the consolidation master name for the given _key_. If there is
 no consolidation master, then +nil+ is returned.