# File lib/plugins/command_plus.rb, line 12
    def alias_command(arg)
      original, new = arg.split(/\s+/)
      if @commands[original.to_sym]
        @commands[new.to_sym] = @commands[original.to_sym].clone
        @commands[new.to_sym].name    = new.to_sym
        @commands[new.to_sym].aliases = []
        @commands[new.to_sym].help    = ''
        puts "alias '#{original}' to '#{new}'."
      else
        raise "#{original} command is not found."
      end
    end