Our startup takes a third approach: automatically detect when one document is a new version of another, so that software can take care of the version control, while the humans can go on being human.

We're bringing version control to people who collaborate by email, starting with Gmail. All people have to do is exchange drafts by email (like normal!), and we infer the history, as if they've been using git.

We're looking for beta testers:

https://draftable.com