Rename pathes fetched and copied as flake inputs (and if it is just for error reporting/stacktraces)

[NobbZ]

Is your feature request related to a problem? Please describe.

When reading any logs or errors created by a flake evaluation, I see errors that include cryptical store pathes which all are named source. It takes some effort and experience to be able to say, if this error is currently pointing to a file from self, nixpkgs or home-manager input, even worse if one uses different versions of nixpkgs in the same flake.

Describe the solution you'd like

Instead of all naming all created store pathes source, use the inputs attribute name by default and add an attribute name to override it by the user.

Additional context

I have not yet thought about a good solution for inputs of inputs.

[tejing1]

Perhaps an alternative would be to have the nix error reporting code back-convert the store paths into the corresponding input of the flake in question. Not sure how you'd pick one in cases where there were multiple inputs referring to the same storepath, though (such as when using follows).

[NobbZ]

TIL: there is a related RFC: NixOS/rfcs#123