add persistent undo functionality to both neovim and vim

nvim/.config/nvim/init.lua

@@ -70,6 +70,12 @@ vim.cmd [[
     set errorformat^=[----]\ %f:%l:\ %m
 ]]
 
+vim.o.undofile = true
+vim.o.undodir = vim.fn.expand("~/.vim/neoundodir")
+if vim.fn.isdirectory(vim.o.undodir) == 0 then
+  vim.fn.mkdir(vim.o.undodir, "p")
+end
+
 vim.keymap.set('n', ',cf', function()
     local qf = vim.fn.getqflist()
     for i, item in ipairs(qf) do

vim/.vimrc

@@ -33,6 +33,13 @@ nnoremap H ^
 nnoremap L $
 set autoindent
 set cursorline
+set undofile
+set undodir=~/.vim/undodir
+if !isdirectory(expand('~/.vim/undodir'))
+    call mkdir(expand('~/.vim/undodir'), 'p')
+endif
+set undodir=~/.vim/undodir
+set undofile
 set errorformat^=[----]\ %f:%l:\ %m
 set expandtab
 set exrc