Infer user nixpkgs commit

[nmattia]

The feature I miss at first is that the default pin isn't related to my NIX_PATH at all. It would be nice (for me) if the tool consulted NIX_PATH and set the pin from the commit my current nixpkgs checkout is at.

• @mpickering

I'm not very familiar with NIX_PATH. Mine is set like this:

$ echo $NIX_PATH 
nixpkgs=https://api.github.com/repos/NixOS/nixpkgs-channels/tarball/168cbb39691cca2822ce1fdb3e8c0183af5c6d0d

but I'm guessing most people use channels and the like. Is there a list of the allowed formats, and what people usually have in there?

[mpickering]

I think some heuristics will have to be used. My NIX_PATH points to a local directory where nixpkgs is checked out. So in order to infer a pin the program would have to try to find out what commit it was checked out at and then try to find that commit in one of the remotes.

In your case as you already link to a tarball then that could be used directly.

I'm not sure how channels work exactly.

[erictapen]

I'm also using a local checkout of Nixpkgs with some custom changes ontop and it would be great if niv could use it like I do it with NIX_PATH. Uncommited changes in Nixpkgs would still have an effect.