def output_mapping
      @output_mapping ||= (
        hash = {}
        case output
        when Array
          output.each do |path|
            hash[path] = format(path)
          end
        when String
          hash[output] = format(output)
        when Hash
          hash = output
        end
        hash
      )
    end
def output_mapping
      @output_mapping ||= (
        hash = {}
        case output
        when Array
          output.each do |path|
            hash[path] = format(path)
          end
        when String
          hash[output] = format(output)
        when Hash
          hash = output
        end
        hash
      )
    end
Convert output into a hash of `file => format`.

 @todo Should we use #apply_naming_policy ?

 @return [Hash]