API to update watched directories

[lptr]

Instead of FileWatcher.startWatching() / stopWatching() we could also have an API to updateWatching() that would simply overwrite the set of watched directories.

Say, we are currently watching ["/usr/local", "/usr/bin"] and we want to watch ["/usr/bin", "/opt"] instead. With the existing APIs the transition requires the client code to diff the two sets and issue two calls:

watcher.stopWatching([new File("/usr/local")])
watcher.startWatching([new File("/opt")])

Instead, it could do the following single call:

watcher.updateWatching([new File("/usr/bin"), new File("/opt")])