Use Object.assign over defaults.

[wtgtybhertgeghgtwtg]

Summary
Drops the defaults package and uses Object.assign. While

this.config = Object.assign({}, DEFAULTS, this.config);

is a little less obvious than

defaults(this.config, DEFAULTS);

I thought it might be worth making a PR.

Test plan
Since it's an internal, no tests have been added that strictly test this.

[wtgtybhertgeghgtwtg]

Travis failing because ember-cli is not resolving.

[bestander]

I understand that defaults mutates the object instead of creating a copy.
Would it be a problem when passing a particular property across modules?

[wtgtybhertgeghgtwtg]

It might if you're sharing a config object between registries and relying on outside mutations.

[bestander]

Could you check if this is the case for the options added here?

[wtgtybhertgeghgtwtg]

I don't think it is. this.config is initialized as an empty object when a registry is constructed, and its values are loaded from a .ini or a lockfile.
The only case I came come up with is if you have something like

const yarnReg = new YarnRegistry();
await yarnReg.loadConfig();
const config = yarnReg.config.
await yarnReg.loadConfig();
// config and yarnReg.config will be different and may have different values if the lockfile has been edited between `yarReg.loadConfig` calls.

[bestander]

Thanks for looking into this, @wtgtybhertgeghgtwtg

[wtgtybhertgeghgtwtg]

Thank you for merging.

[bestander]

Try rebasing to fix CI test