Update config extend to allow custom logger

[ruimarinho]

This allows using a config.js file with a custom logging function defined.

[ruimarinho]

@sdepold I'm having trouble setting up a test case for this. It doesn't seem to fit in migrate.test.js yet it needs most of its boilerplate code from prepare.

[sdepold]

@ruimarinho the tests are currently still in a pretty shitty shape and needs to be refactored. I will do this during the next days/week. For now, feel free to just copy and paste the prepare block.

[sdepold]

plus: good catch!

[ruimarinho]

I tried to, but I think I'll wait for the refactor because right now it's pretty complicated to get around the tests. I'm a big advocate for gulp, but do you think it's the right approach in this case? I've had nothing but good experiences with a thin cli based off individually tested library code.

[sdepold]

Not sure if I understand you :D We discussed yesterday, that we will move the gulp tasks itself into a separate project and just use the tasks then in the cli

[sdepold]

Tbh. I actually wonder how you would ever configure the logging as you cannot define a function within json... Anyway, I wrote a test for it and merged the PR.

[ruimarinho]

@sdepold sorry for the delay, I was on vacations. I'm using a js configuration file, not a json one :) what I meant regarding gulp was that maybe the tests are too low-level by testing stdout. If you had tested functions return values, maybe it'd be easier to test them like a regular script?