I broke up with neovim....vim is my best friend now

dot_vim/plugged/vim-airline/autoload/airline/extensions/undotree.vim

@@ -0,0 +1,29 @@
+" MIT License. Copyright (c) 2013-2021 Bailey Ling et al.
+" Plugin: https://github.com/mbbill/undotree
+" vim: et ts=2 sts=2 sw=2
+
+scriptencoding utf-8
+
+if !exists(':UndotreeToggle')
+  finish
+endif
+
+function! airline#extensions#undotree#apply(...)
+  if exists('t:undotree')
+    if &ft == 'undotree'
+      if exists('*t:undotree.GetStatusLine')
+        call airline#extensions#apply_left_override('undo', '%{exists("t:undotree") ? t:undotree.GetStatusLine() : ""}')
+      else
+        call airline#extensions#apply_left_override('undotree', '%f')
+      endif
+    endif
+
+    if &ft == 'diff' && exists('*t:diffpanel.GetStatusLine')
+      call airline#extensions#apply_left_override('diff', '%{exists("t:diffpanel") ? t:diffpanel.GetStatusLine() : ""}')
+    endif
+  endif
+endfunction
+
+function! airline#extensions#undotree#init(ext)
+  call a:ext.add_statusline_func('airline#extensions#undotree#apply')
+endfunction