nix-shell complains about nixos channel being a symlink

[leona-ya]

Describe the bug

We have a custom nixos channel which contains nixpkgs as a subfolder among others. -> We have /nix/var/nix/profiles/per-user/root/channels/ as a symlink to the nixos subfolder of a store folder. (e.g. /nix/store/49qpgqzyvk0r87mi1g6j376ardmzkvkq-nixos/nixos)

nix-shell <nixpkgs> -A hello now fails with

error: path '/nix/var/nix/profiles/per-user/root/channels/nixos' is a symlink

Steps To Reproduce

• Use /nix/store/iidn0ph0jfcfqsmxmdxxczxa85wxrfqd-release-24.11.5308.2542d813/tarballs/nixexprs.tar.xz as channel (download from s3.whq.fcio.net/hydra)
• run the above command

Expected behavior

A valid nix-shell spawns.

Metadata

nix-env (Nix) 2.25.2

Additional context

I didn't found a release note about this since 2.18 (the last version we tested with which it worked)

Checklist

• checked latest Nix manual (source)
• checked open bug issues and pull requests for possible duplicates

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[leona-ya]

Interestingly, this works on 2.26 (even though I didn't find anything in the release notes). But it's quite slow because it

unpacking 'https://github.com/NixOS/nixpkgs/archive/573c650e8a14b2faa0041645ab18aed7e60f0c9a.tar.gz' into the Git cache...

and i'm really unsure why it does that, because the necessary files should already be on the machine? (probably not in the git cache tho).