feat: simplify flake.nix

modules/darwin/nix-core.nix

@@ -0,0 +1,41 @@
+{
+  pkgs,
+  lib,
+  ...
+}: {
+  ###################################################################################
+  #
+  #  Core configuration for nix-darwin
+  #
+  #  All the configuration options are documented here:
+  #    https://daiderd.com/nix-darwin/manual/index.html#sec-options
+  #
+  ###################################################################################
+
+  # enable flakes globally
+  nix.settings.experimental-features = ["nix-command" "flakes"];
+
+  # Allow unfree packages
+  nixpkgs.config.allowUnfree = true;
+
+  # Auto upgrade nix package and the daemon service.
+  services.nix-daemon.enable = true;
+  # Use this instead of services.nix-daemon.enable if you
+  # don't wan't the daemon service to be managed for you.
+  # nix.useDaemon = true;
+
+  nix.package = pkgs.nix;
+
+  programs.nix-index.enable = true;
+
+  # boot.loader.grub.configurationLimit = 10;
+  # do garbage collection weekly to keep disk usage low
+  nix.gc = {
+    automatic = lib.mkDefault true;
+    options = lib.mkDefault "--delete-older-than 1w";
+  };
+
+  # Manual optimise storage: nix-store --optimise
+  # https://nixos.org/manual/nix/stable/command-ref/conf-file.html#conf-auto-optimise-store
+  nix.settings.auto-optimise-store = true;
+}