[cfe-dev] RFC: A virtual file system for clang

[Rafael Avila de Espindola]

> The idea is to abstract the view of the file system using an AbstractFileSystem class that mimics the llvm::sys::fs interface:
> 

My only request is to add functionality as you go. llvm:sys:fs initially had a lot more functionality than what was used by llvm or clang and I am sure there still some left.

Please also use the opportunity to modernize the API when possible (using ErrorOr for example).

Cheers,
Rafael