visionmedia/commander.js — pull request #212 by Jeremial (2014-04-13 15:43:55+00:00)
Title: remove `subcommand --help` output comma when more than one arg

supose I have defined a program `app` below
```js
var program = require('commander');

program
.version('0.0.1');

program
.command('exec [arg2]')
.description('exec example')
.action(function(arg1, arg2, options){
console.log('called exec');
});

program.parse(process.argv);
```

Then when I get the exec help info via `app exec --help`, it will output
```bash
Usage: exec [options] ,[arg2]

Options:

-h, --help output usage information
```

But the right output should be
```bash
Usage: exec [options] [arg2]

Options:

-h, --help output usage information
```

So, I find the problem is that the `args` is an array, when its length is larger than 1, it will join with `,`, what I do is join the array with space :)