yes there's a bit of java in my nvim config why do you ask?

lua/conf/plugins/undotree.lua

@@ -0,0 +1,12 @@
+local misc = require('core.misc')
+local map = misc.map
+
+return { 'mbbill/undotree',
+  function()
+    if (vim.g.loaded_undotree) then
+      vim.g.undotree_DiffAutoOpen = 0
+    end
+
+    map("n", "<leader>u", "<cmd>UndotreeToggle<CR>")
+  end
+}