At facebook, a virtual filesystem (https://github.com/facebookexperimental/eden https://github.com/facebookexperimental/eden) + change monitor (https://facebook

At facebook, a virtual filesystem (https://github.com/facebookexperimental/eden https://github.com/facebookexperimental/eden) + change monitor (https://facebook.github.io/watchman/ https://facebook.github.io/watchman/) = source control operations run in O(files I have modified) instead of O(size of repository) time