File watching service

 Watchman can be used to watch files and record when they actually change.
 It can be used to trigger actions (such as rebuilding assets) when
 matching files change. If you require to perform an action based on
 whether a file changes or not, watchman may be the tool you need. By
 giving watchman a pattern and an action to take when the files change,
 you can trigger an activity to be taken.