Create parameterized top-level entry point

nixos/default.nix

+# This is the entry point for my NixOS configuration.
+{ layers ? [] }:
 { lib, config, pkgs, ... }:
 
+let
+  layerImports = map (l: ./layers + "/${l}.nix") layers;
+in
 {
   imports = [
     ./modules
-  ];
+  ] ++ layerImports;
 
   nixpkgs.config = {
     packageOverrides = ( import ./pkgs ) { inherit lib config; } ;

nixos/layers/base.nix

@@ -4,7 +4,6 @@
 
 {
   imports = [
-    ./..
     ./zsh.nix
   ];