I am using Vim 7.4. According to vim's help on persistent undo:
An undo file is also ignored if its owner differs from the owner of the edited file.
Set 'verbose' to get a message about that when opening a file.
Where do I set
verbose? In my vimrc I have the following as my persistent undo-related code:
verbose set undodir=~/.vim/temp_dirs/undodir
echomsg "ERROR: undodir does not exist or is not writable."
verbose set undofile
However, when I edit a file of which I am not the owner, I get no such message.