default.nix: init

[wegank]

This PR moves the packaging logic from flake.nix to default.nix, so that all packages, including overview and options, can be built with nix-build -A some-package, and be evaluated with nix repl --file ..

In addition, helper functions introduced in flake.nix in the previous refactor are moved to helper.nix, which also accepts nix repl --file helper.nix, making flake.nix even simpler.

[fricklerhandwerk]

Blocked on #222

[fricklerhandwerk]

Is there any reason we can't create the actual values here already?

Suggested change

	nixpkgs ? inputs.nixpkgs,
	pkgs ? import inputs.nixpkgs { inherit system; config = {}; overlays = []; },

[wegank]

There's the Rust overlay, I guess passing a different pkgs could break atomic-server?

[wegank]

Though I have no idea why the overlay is there, I'll open a test PR to see what happens if it's removed.

[fricklerhandwerk]

If you have pkgs from arguments you get

Suggested change

	lib = import (nixpkgs + "/lib");
	inherit (pkgs) lib;

[wegank]

Since lib is system-agnostic, I guess inheriting it from a system-dependent pkgs is overkill.

[cleeyv]

I've been trying out this default-nix-init branch as part of testing the use of deploying NGIpkgs software with npins over at https://github.com/ngi-nix/npins-ngipkgs.

Although I haven't gotten it working yet, since it can already be used to build packages I assume that it will be feasible to use this proposed default.nix to deploy packages from NGIpkgs to NixOS using npins. However, I get the impression that there would be more substantial changes required in order to use it to deploy projects from NGIpkgs, which is currently one of the features of flake.nix version via nixosModules. Do you have a sense of how feasible it might be to implement something comparable for the default.nix as well?