flake-parts/setups: update shared Nix config

At least we've set the right sources for the system's nixpkgs and
home-manager branches.

configs/flake-parts/default.nix

@@ -17,30 +17,6 @@
   _module.args = {
     # This will be shared among NixOS and home-manager configurations.
     defaultNixConf = { config, lib, pkgs, ... }: {
-      # I want to capture the usual flakes to its exact version so we're
-      # making them available to our system. This will also prevent the
-      # annoying downloads since it always get the latest revision.
-      nix.registry =
-        lib.mapAttrs'
-          (name: flake:
-            let
-              name' = if (name == "self") then "config" else name;
-            in
-            lib.nameValuePair name' { inherit flake; })
-          inputs;
-
-      nix.settings.nix-path =
-        (lib.mapAttrsToList
-          (name: source:
-            let
-              name' = if (name == "self") then "config" else name;
-            in
-            "${name'}=${source}")
-          inputs
-        ++ [
-          "/nix/var/nix/profiles/per-user/root/channels"
-        ]);
-
       # Extend nixpkgs with our overlays except for the NixOS-focused modules
       # here.
       nixpkgs.overlays = lib.attrValues inputs.self.overlays;

modules/flake-parts/setups/home-manager.nix

@@ -200,6 +200,7 @@ in
       type = with lib.types; attrsOf (submoduleWith {
         specialArgs = { inherit (config) systems; };
         modules = [
+          (import ./shared/nix-conf.nix { inherit inputs; })
           ./shared/nixvim-instance-options.nix
           ./shared/config-options.nix
           configType

modules/flake-parts/setups/nixos.nix

@@ -459,11 +459,6 @@ let
             {
               nixpkgs.overlays = setupConfig.overlays;
               networking.hostName = lib.mkDefault setupConfig.hostname;
-
-              nix.settings.nix-path = lib.mkBefore [
-                "home-manager=${inputs.${setupConfig.homeManagerBranch}}"
-                "nixpkgs=${inputs.${setupConfig.nixpkgsBranch}}"
-              ];
             }
 
             (lib.mkIf (setupConfig.domain != null) {
@@ -489,6 +484,7 @@ in
       type = with lib.types; attrsOf (submoduleWith {
         specialArgs = { inherit (config) systems; };
         modules = [
+          (import ./shared/nix-conf.nix { inherit inputs; })
           ./shared/config-options.nix
           ./shared/nixvim-instance-options.nix
           configType

modules/flake-parts/setups/shared/nix-conf.nix

@@ -0,0 +1,39 @@
+{ inputs }:
+
+{ config, lib, ... }:
+
+let
+  inputs' = inputs // {
+    nixpkgs = inputs.${config.nixpkgsBranch};
+    home-manager = inputs.${config.homeManagerBranch};
+  };
+in
+{
+  config.modules = [(
+    { lib, ... }: {
+      # I want to capture the usual flakes to its exact version so we're
+      # making them available to our system. This will also prevent the
+      # annoying downloads since it always get the latest revision.
+      nix.registry =
+        lib.mapAttrs'
+          (name: flake:
+            let
+              name' = if (name == "self") then "config" else name;
+            in
+            lib.nameValuePair name' { inherit flake; })
+          inputs';
+
+      nix.settings.nix-path =
+        (lib.mapAttrsToList
+          (name: source:
+            let
+              name' = if (name == "self") then "config" else name;
+            in
+            "${name'}=${source}")
+          inputs'
+        ++ [
+          "/nix/var/nix/profiles/per-user/root/channels"
+        ]);
+      }
+  )];
+}