Decouple Execution from Parsing

[BenjaminHolland]

This library shouldn't tightly couple argument parsing and command execution. This is a mistake every cli library seems to make, at the expense of making the library generally useful. Parsing command-like strings into arbitrary types should arguably be explicitly the focus, with an optional layer for "automatic" executions of commands. In particular, use cases that involve REPL's, like bots, suffer from this coupling.

The results of parse should be either an instance of the filled out subcommand data or an error state. In addition. usage information should be publicly queryable to support custom usage displays (i.e. a version of makeUsage that returns an html snippet)

#48

[anti-social]

Have the same thoughts: #45 (comment)

[beretis]

This would be really great. Im working on an app, which has CLI api, but it has run loop, and I don't wanna terminate the process ever. I tried to subclass ArgParser, but the fact that internal var outputAndTerminate is internal means, that I cant even bend it my way :/
Now I have to implement parsing arguments on my own.