Watchman doesn’t need introduction if you have done Compass, Susy or Sass. Simply put it’s a node module; an observer for picking up any changes in the filesystem at a specified location to afterwards, trigger an action based on it. Typically it is sued to transpile your .scss files into .css files. For some reason I’m unable to install it via npm command. So I got around to write the instructions to build it from its source.
$ git clone https://github.com/facebook/watchman.git
$ cd watchman
$ git checkout v4.5.0 # for the latest stable version
$ sudo make install