Using overlay filesystem for "other" files idea

Hello,

I got following idea.

If different branches seriously differ and you switch branches, then it's more likely you will loose most part of build files (e.g. when run build). Also in projects that may have some bugs in build system (e.g. buggy makefiles) there is a chance you will not get clean build environment. E.g. somebody forgot to add include file as dependency in Makefile --- oops, you're in trouble. Even without bugs in build system, some temp files are overwritten each time you run build for a custom branch.

I think using overlays for other files can help much to solve this issue. You can have git repository in regular directory (like now) and overlay fs mounted over this repository (for each branch its own overlay). Another benefit is clearing source tree after build.

What do you think, guys? If it sounds good, I could work on this, maybe even on my work.