code: def ls(mask = '', raise = true)
        ls_items = []
        mask = '"' + mask + '"' if mask.include? ' '
        output = exec 'ls ' + mask
        output.lines.each do |line|
          ls_item = LsItem.from_line(line)
          ls_items << ls_item if ls_item
        end
        ls_items
      rescue Client::RuntimeError => e
        raise e if raise
        []
      end
docs: List contents of a remote directory
   @param [String] mask The matching mask
   @param [Boolean] raise If set, an error will be raised. If set to
   +false+, an empty array will be returned
   @return [Array] List of +mask+ matching LsItems