If an external entity changes the file you're currently editting ...

It seems that it will show you (when you're focused on it again - not sure how it would react if you're already looking at the file) and shows you a diff that looks like what you see when you do a merge/rebase in git and have a conflict!

I'd never seen that before. Since I knew what changed it (me, from the terminal), I just exitted the editor, as I didn't know what had happened and it looked like the git conflict markup. I went right back in to it and the "conflicted" area wasn't there, so it was just showing what had changed, which is kind of cool.

I'll have to try it again some time to see if it still does that, but it's a cool feature, if so.