Which project files are relevant for source control?

I want to setup a proprietary configuration management system, means outside unreal editor, for example using MS TFS, ClearCase, or GIT, covering a wider scope e.g. containing content files of external tools, which of the files regarding unreal engine 4 project are relevant the set under source control, in terms of not being able to be generated by the unreal editor system?

Is there somewhere a description available, may be in the future?

I found a .gitignore on github which works pretty well for me. You might want to check out https://github.com/samsheff/UE4-Gitignore