How do I make vim's undo buffer persistent across sessions?

Question

When I make an edit to a file and then leave vim, I would like to be able to undo that change when I reopen it later.

Answer 1

You can turn on persistent undo, check the help with

:help undo-persistence

At least vim 7.3 is required.

undo-persistence needs some setup before use, like defining a directory to keep the persistent undo information. A good explanation is given here: http://amix.dk/blog/post/19548 (thanks to @Dalker)

Answer 2

I can't comment on the post above, but I'd like to point out that undo-persistence is not available in vim 7.2, which is the version installed by default in Ubuntu 10.10, so probably in many people's computers at the time of this post.

Once vim is upgraded to 7.3, undo-persistence needs some setup before use, like defining a direcory to keep the persistent undo information. A good explanation is given here: http://amix.dk/blog/post/19548