Descriptions and default values

[mnapoli]

This PR brings support to set descriptions and default values:

$app->command('greet firstname? lastname?', function () {
    // ...
});

$app->defaults('greet', [
    'firstname' => 'John',
    'lastname'  => 'Doe',
]);

$app->descriptions('greet', 'Greet someone', [
    'name'   => 'Who do you want to greet?',
    '--yell' => 'If set, the task will yell in uppercase letters',
]);

[brandisher]

@mnapoli Thanks for looking into the defaults and descriptions, they'll be a big improvement. I do think that there should be a more fluid way to add them. Descriptions would almost always be necessary, so I think either defining them as a parameter in the command() call or as a chained method would make the most sense.

With defaults, I think a chained method makes the most sense.

Both descriptions and defaults are tied directly to the command so I think method chaining is the best methodology for both. I'd be happy to assist if need be. My time is sort of limited but I really like the style of this project, kind of like Slim for cli :-)

[mnapoli]

@cwscribner so with the same example that would be:

$app->command('greet firstname? lastname?', function () {
    // ...
})->defaults([
    'firstname' => 'John',
    'lastname'  => 'Doe',
])->descriptions('Greet someone', [
    'name'   => 'Who do you want to greet?',
    '--yell' => 'If set, the task will yell in uppercase letters',
]);

Is that what you had in mind?

[brandisher]

Precisely! I definitely like the descriptions() parameter organization. Since it's called as a chained method, it totally makes sense for the function signature to be descriptions(string $commandDescription, array $parameterDescripitions). Very clean :-)

[mnapoli]

OK that's fine by me, I'll try to update my PR when I have time (going on holidays soon ;))

[mnapoli]

All done, @cwscribner syntax updated with the fluent interface.