To elaborate on the other comments, it is extremely easy to use the op log to undo basically anything.

I was live demoing something and performing some manual repo surgery in order to demonstrate some thing that can happen with git but is nicely solved by jj. In doing the surgery I absolutely fucked everything.

I had never used the undo feature or the op log before. In less than five minutes—during the live demo—I was able to figure out how to reset things back to a known good state. It was stupidly easy.