nixpkgs.flake.setFlakeRegistry

Whether to pin nixpkgs in the system-wide flake registry (/etc/nix/registry.json) to the store path of the sources of nixpkgs used to build the nix-darwin system.

This is on by default for nix-darwin configurations built with flakes.

This option makes nix run nixpkgs#hello reuse dependencies from the system, avoid refetching nixpkgs, and have a consistent result every time.

Note that this option makes the nix-darwin closure depend on the nixpkgs sources, which may add undesired closure size if the system will not have any nix commands run on it.