Spinning off of #1080 (comment)

if you provide a tsconfig without "includes" (or "files"), I.e. an empty tsconfig: {}, then typescript uses a different codepath to setup the folder watchers.
Triggering a directory change does not work the same was as when the tsconfig has "includes".

It won't block the release on Monday, as it's an edge case of sorts, but I'll need to look deeper into it to figure out how it all works!