[5.3] add $default parameter to query builder when() method

[tomschlick]

Originally opened in #15421 but @themsaid asked I open it against master

This allows you to specify a default closure to run if the when() $value attribute is false.

I recently found myself creating a sorting / filtering system with defaults that the user could change. Without this you would have to do all kinds of wackiness to clear the previous where() clause on $value being true.

Here is an example of this in action

Time::when($request->has('type'), function ($query) use ($request) {
    return $query->where('type', $request->input('type'));
}, function ($query) {
    return $query->where('type', 1);
})
->get();

[tomschlick]

Looks like composer is having some issues on Travis... Any way to schedule a rebuild on that?

[taylorotwell]

Do you want to send this to 5.3?

[tomschlick]

Ugh, this branch switcher from GH sucks. I'll re-submit.

[themsaid]

@tomschlick I was the reason for all this opening/closing hassle, sorry :)

[tomschlick]

No problem haha