>I believe the important thing to preserve in history is whatever your unit of review is

I do not share that belief, but this thread (your posts and others) gave me an idea about code reviews. They became commonplace when I'd been working in software for a while already and, while I see the benefits, I never really felt like I handled them well. I guess one of the ingredients for handling them better is to center the workflow around them - an area in which I have never noticed major changes in an existing project, although they are visible when looking from the right angle: Long-lived, large feature branches have become noticeably less common.