Issue Type

• [x ] Feature Request

Expected

I'd like to be able to do the following:

cli.command("echo [arg]", "echo the input back", { variadic: true }).action((arg: string[]) => {
  console.log(arg);
  console.log(arg.join(" "));
});

$ cli this is a message
[ "this", "is", "a", "message" ]
this is a message

$ cli "this is a message"
[ "this is a message" ]
this is a message

In other words, allow the final argument of a command to be marked as variadic without the spread operator. This would make things a little more ergonomic when working with commands where you're input sentences/longer strings - you could do either.

Actual

Currently, the behavior is of course available, but we need to use the spread operator convention.

cli.command("echo [...arg]", "echo the input back").action((arg: string[]) => {
  console.log(arg);
  console.log(arg.join(" "));
});

The issue with this convention is that [...arg] seems to be imply that the arguments are separate conceptual units.

cli

Usage:
  $ cli <command> [options]

Commands:
  echo [...arg]   echo the input back  

For more info, run any command with the `--help` flag:
  $ sample-cli echo --help

This is not the case when we're entering single sentences, where a set of strings is separated by spaces. It's nice to just be able to do $ cli echo this is a sentence that I want to type unquoted.