refactor(nvim): update git nix code

homeManagerModules/neovim/git/default.nix

@@ -1,4 +1,14 @@
-{pkgs, ...}: {
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}: let
+  inherit (lib) mkIf;
+
+  cfg = config.programs.neovim;
+in {
+  config = mkIf cfg.enable {
     programs.neovim.plugins = [
       pkgs.vimPlugins.fugitive
 
@@ -24,4 +34,8 @@
           '';
       }
     ];
+  };
+
+  # For accurate stack trace
+  _file = ./default.nix;
 }