I think non-trivial quality github activity over a sustained period of time would be an excellent indicator of the type of persistence that I'm thinking of, and

I think non-trivial quality github activity over a sustained period of time would be an excellent indicator of the type of persistence that I'm thinking of, and something that a candidate could pretty easily work into an interview answer in a positive light. Plus, even if they don't use it to break a tie in an "all else equal" interview, the contributions themselves will make the candidate a stronger candidate.