refactor(nixos): inline module enable conditions

configs/nixos/modules/shell/git.nix

@@ -5,14 +5,13 @@
 }:
 # git for the primary user, configured through home-manager.
 let
-  cfg = config.modules.shell.git; # NOLINT(let_order)
   user = config.user.name;
 in
 {
   options.modules.shell.git.enable =
     lib.mkEnableOption "git for the primary user, carrying the operator's commit identity";
 
-  config = lib.mkIf cfg.enable {
+  config = lib.mkIf config.modules.shell.git.enable {
     home-manager.users.${user}.programs.git = {
       enable = true;