I often go into a Git worktree of one of my projects and mess around a bit to try something out. If I find it's not working, I tell git to discard the changes with git checkout . and git clean -df. What I'm saying is exactly “on second thought, don’t do anything" - while what happens in practice is that Git restores all files to their HEAD status and removes all the new files that are not already in HEAD.

Of course, the difference is that I already have all the work I want to keep under source control, so these changes I've discarded really were that - just changes. He, on the other hand, "was just playing with the source control option" - so these "changes" he was discarding really were all his work. But Git did not know that.