Enhanced undo and redo with a undodir
Configuring your vimrc to use a undodir
Since vim version 7.3 the feature 'persistent_undo' is supported, which makes it possible do undo/redo changes, even after closing vim or restarting your computer.
It's possible to configure it by adding the following to your vimrc, but first create a directory, where your undofiles should be saved. You can create the file anywhere, but I recommend using the ".vim" directory.
After adding this to your vimrc and sourcing the vimrc again, you can use the feature by using the basic undo/redo commands