Shooting myself in the foot with Git by accident

> This isn't the first time I've accidentally done two overlapping 'git pull' operations on the same repository. I think it's the first time I hit this error...

If these are two separate clones / checkouts, how can running `git pull` on both conflict?

I keep multiple copies of some repos, but I can't recall ever pulling both at once. I would expect it to work: separate folders, indexes, and git processes.