[Nix-dev] env-manifest-ception.nix

[Layus]

Hi,

Today I fixed an issue that bugged me for some months by using `nix-env 
-e env-manifest.nix` !
The main issue was a full root partition :-).

I have no idea how my system got that messed up, probably some 
copy-paste error when doing a nix-env -i /nix/store/something.

I just wanted to share the funny side of such a stupid error, but you 
are welcome to comment on how to avoid that, if at all desirable.

Guillaume.