Retain undo buffer after quitting VIM?

I'm wondering if it is possible to retain VIM's undo buffer after quitting.

For example, I'd like to make some edits to a file, save & quit (:wq), then reopen the file and still be able to hit 'u' to undo the开发者_如何学Go edits. Is this possible in VIM?

That isn't currently possible. There is an item in the TODO list and there was a proposed patch on the development mailing list, though.

Updated 2010/6/6: The pre-release work on Vim 7.3 has included the persistent undo patch.

You probably already know it, but in most cases you can just save, then Ctrl-Z to go to the shell, and then fg to return to vim.