Error: lib.fileset.gitTracked: Expected the argument (/mnt/nix/store/<hash>-source) to point to a local working tree of a Git repository, but it's not

Hi!

I moved my boot partition to the end of my disk hence I deleted the old boot partition and created a new one at the new position.
Now I needed to update that to my system.
In the ISO I updated my hardware-configuration.nix with nixos-generate-config --show-hardware-config --root /mnt > <destination in my flake> and afterwards I executed

sudo nixos-install --root /mnt --flake <path>#<hostname>

however, I got the following error message afterwards:

error: lib.fileset.gitTracked: Expected the argument (/mnt/nix/store/<hash>-source) to point to a local working tree of a Git repository, but it's not.

How can I fix this?

Ok, the issue seems to be coming from an input (helix) but I can’t reproduce this from a “healthy” system (aka: System which is currently running fine).