This may be by design, but I would have expected calling:

command <unknown-sub-command> 

...to fail. But instead it just exits immediately, this can lead to confusion when tired as you might think your command isn't working, but instead it's just spelt incorrectly.

Is there a flag or something to enable this error. Or should I just make a white list of known commands and fail when the first parameter isn't a known sub command?