refactor deprecate command and add tests

[nlf]

refactoring was mostly for readability, but there are some important changes to completion.

notably, the api endpoint we were using to list packages doesn't exist so could never work. i adjusted it to use a method that works, and to filter the result set based on current partial user input. i'm not totally sure if the filtering is necessary, but it seems kind to do it in js-land instead of letting the shell deal with it when the number of packages could be significant

References

Closes npm/statusboard#146

[ljharb]

When you say "list packages" - does that mean there's supposed to be a way for npm deprecate to list current deprecation messages? (I ask because I'd love to see https://npmjs.com/deprecations become obsolete). I could file an RFC for this if it's not a thing that's supposed to exist.

[nlf]

When you say "list packages" - does that mean there's supposed to be a way for npm deprecate to list current deprecation messages? (I ask because I'd love to see https://npmjs.com/deprecations become obsolete). I could file an RFC for this if it's not a thing that's supposed to exist.

ah, nope. this was for tab completion, npm deprecate <tab> was intended to list every package you have write access to but was broken, this fixes it.

what you're suggesting would need an RFC, but is a pretty easy one for implementation.

[ljharb]

Thanks, I'll add that to my list then.