Smart incremental build mode

[RoHePu]

Do you want to request a feature or report a bug?
feature

What is the current behavior?
Using webpack-dev-server no information on the files that was changed seems to be passed to webpack. Every incremental build in webpack seems to start from the entry points and traverses all modules. This is a bottle neck for incremental builds having a huge amount of modules.

If the current behavior is a bug, please provide the steps to reproduce.
We have created a repo where you can produce as many JS files as you want to test the performance of webpack.

What is the expected behavior?
We would wish to have an intelligent incremental build mode that touches the changed files only.

If this is a feature request, what is motivation or use case for changing the behavior?
All projects having a huge amount of modules would love it because it would decrease the incremental build times tremendously. Incremental build times longer than 15 sec are a pain for developers.

Please mention other relevant information such as the browser version, Node.js version, webpack version and Operating System.
Afaik all webpack versions are affected.