History and evidence of cheating?

I gave my students an assignment, but when I roll back history to the beginning, I’m finding files already have many lines of code.

If they created the files, shouldn’t, at the very beginning, I see nothing at all? Even if they pasted something in? Or is there some limit as to how far back history goes?

They might have created a file with that name, typed a bunch of code, deleted the file, and finally recreated the file. I don’t think history goes further back than that… Now that I think about it, that’s a very easy way to cover up cheating.