neovim: add peristant undo file

home/neovim.nix

@@ -1,5 +1,7 @@
 { pkgs, lib, inputs, config, ...}:
-{
+let
+  undoDir = "${config.home.homeDirectory}/.vim/undo";
+in {
   programs.neovim = {
     enable = true;
     defaultEditor = true;
@@ -41,6 +43,11 @@
       set tabstop=2
       set expandtab
 
+      set undofile
+      set undodir=${undoDir}
+      set undolevels=1000
+      set undoreload=10000
+
       " Integrate status with lightline
       let g:lightline = {
         \   'active': {
@@ -117,4 +124,7 @@
       map <Leader><Space> :noh<CR>
     '';
   };
+
+  # Create undo directory
+  home.activation.vimUndoDir = lib.hm.dag.entryAfter ["writeBoundary"] "mkdir -p ${undoDir}";
 }