eachSystemPassThrough should use some form of deep update

[jzbor]

The example below should give two nixosConfigurations - one for each system. Instead only the last one is generated. If this is the intended behavior this is not reflected in the documentation (https://github.com/numtide/flake-utils#eachdefaultsystempassthrough--system---attrs).

flake.nix to reproduce:

{
  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = { self, nixpkgs, flake-utils }: flake-utils.lib.eachSystemPassThrough [ "x86_64-linux" "aarch64-linux" ] (system: {
    nixosConfigurations."default-${system}" = nixpkgs.lib.nixosSystem {
      inherit system;
    };
  });
}

nix flake show:

path:/home/(...)
└───nixosConfigurations
    └───default-aarch64-linux: NixOS configuration