formatted_usage (Thor::Options)

    # File lib/thor/options.rb, line 161
        def formatted_usage
          return "" if @switches.empty?
          @switches.map do |opt, type|
            case type
            when :boolean
              "[#{opt}]"
            when :required
              opt + "=" + opt.gsub(/\-/, "").upcase
            else
              sample = @defaults[undasherize(opt)]
              sample ||= case type
                when :optional then undasherize(opt).gsub(/\-/, "_").upcase
                when :numeric  then "N"
                end
              "[" + opt + "=" + sample.to_s + "]"
            end
          end.join(" ")
        end