Fail when using same command and alias

[ajfranzoia]

Fixes #490. Prevents running a command twice when -accidentally- using same command alias and name.

[deian]

LGTM. Thanks for doing this. The only thing I would point out is a style difference: it seems like the rest of the file doesn't use curly braces for a single-statement if. (Though I'm in no position other than to informally comment.)

[ajfranzoia]

@SomeKittens Let me know if there's anything that needs modification (same for #492 and #494)

[hellowin]

@ajfranzoia I think what @deian said is, you just need to change

if (alias === this._name) {
  throw new Error('Command alias can\'t be the same as its name');
}

to

if (alias === this._name) throw new Error('Command alias can\'t be the same as its name');

[abetomo]

@ajfranzoia
Could you please resolve the conflict?

[ajfranzoia]

@abetomo done!

[abetomo]

Thank you!