[lmm]

So what happens when two developers edit the same file, or make changes to different files that in combination break the system?

You need commits, you need the ability to merge. If you don't want to force all commits to happen online and everyone to resolve conflicts immediately then you need branches. You want tags if you're going to have releases (otherwise how do you refer to them?). At that point you basically have git.

All the complicated features were added because someone thought they needed them (there are certainly a few git features where I think that someone was wrong, but not many).