I have a Google Form that I ask all students to fill out. That’s a chance for me to survey them on a variety of basic questions, and also to just say “tell me your campus NetID and your GitHub ID”. Last semester, this mostly worked fine, except I had one student who changed their GitHub ID mid-semester, because whatever, so I had to tweak my scripts a bit.
As a matter of redundancy, I also require them to place their name and campus NetID in the README.md file. Most do it, a few forget. I suppose I could tweak the Travis CI system to fail the build if it sees the string in the README.md file. That would work wonders.