refactor: restructure

modules/home-manager/modules/nixvim/undotree.nix

@@ -0,0 +1,34 @@
+{ lib, config, ... }:
+let
+  cfg = config.presets.undotree;
+in
+{
+  options.presets.undotree = {
+    enable = lib.mkEnableOption "Undotree";
+  };
+
+  config = lib.mkIf cfg.enable {
+    opts = {
+      undodir.__raw = # lua
+        "os.getenv('HOME') .. '/.config/nvim/undodir'";
+      undofile = true;
+    };
+    keymaps = [
+      {
+        key = "<leader>u";
+        mode = "n";
+        action = "<cmd>:UndotreeToggle<CR>";
+      }
+    ];
+    plugins = {
+      undotree.enable = true;
+      which-key.settings.spec = [
+        {
+          __unkeyed-1 = "<leader>u";
+          desc = "Undotree";
+          icon = "󰕌";
+        }
+      ];
+    };
+  };
+}