Fix stylesheet watcher

[mauricioszabo]

Fixes INotify watches being exhausted when someone on Linux with a lot of packages and files on .pulsar-next directory opens Pulsar

[savetheclocktower]

This is fine, but I really do need a working theory as to how the additional watching of a single directory — even one as potentially deep as the Pulsar home folder — could involve over 40,000 extra inotify watchers.

In theory, both nsfw and @parcel/watcher would need exactly one watcher per directory. So is it possible that you have ~40,000 unique directories below your .pulsar-next folder?

[savetheclocktower]

Ugh. OK, fine:

cd ~/.pulsar-next && find . -type d | wc -l

produces 34582 for me.

compile-cache seems to have lots and lots of unique directories. This is a problem and suggests to me that we should avoid using watchPath on anything within the .pulsar-next folder, at least until we have a way of adding a non-recursive watcher.

[savetheclocktower]

OK, fine by me. Landing this!

(It turns out we have some specific requirements for file-watching that go beyond what src/path-watcher.js can do. I'll probably capture this in a new enhancement issue.)

[mauricioszabo]

Just for the record, my .pulsar-next folder have about 40k directories, and opening Pulsar in some specific project added 22k other watchers... that's how it exploded my watchers :(

Still, this PR keeps the functionality of watching only the stylesheet file that was originally on Atom, so we are not changing anything. But I agree we could benefit of watching a single, non-recursive directory too.