Configure chokidar to use fs.watch instead of fs.watchFile

[thirtyseven]

fs.watch is preferable to fs.watchFile as it uses file change notification instead of stat polling. With large projects, there can be a significant performance improvement.

fs.watch isn't always available, so maybe this should be behind a config option? I think it's a sane default though.

[vojtajina]

@thirtyseven I need to look into this more. While this makes sense, it's not that simple. I'm not sure about inotify (linux), but kqueue (mac) does count these listeners as open file descriptors. Common limit is 256 (which includes file writing/stating/reading) so you can easily hit that limit.

Do you have any more insights? Did you try this on linux/mac? How big project (how many files)?

This is definitely important thing.

Btw, I'm working on making watching more efficient (even with the stat polling).

[vojtajina]

@thirtyseven I added this as an undocumented config option (see 18514d6), so I'm closing this PR.

The problem is that fs.watch still does not work on Mac, we need to fix it first (in node). Then it can be the default option in Karma. See paulmillr/chokidar#62

Thanks for bringing this up!