Can I see changes before I save my file in Vim?

Question

I use Vim. I open a file. I edit it and I want to see what I\'ve edited before I save it.

How can I do this in Vim?

Answer 1

Not exactly what you're looking for but SCMDiff.vim is really cool. One keypress, and it diff-highlights your current file with the head revision in a source control repo. It's meant to work with many SCMS. I use it with perforce.