Re: SSH is the way to go
Maybe I misunderstand? What possible benefit would you gain from using multiple key pairs when the end goal is to authorise access to your code repository? I would only consider that if I needed to (weakly) authenticate or if there was a concern about compromise of one single device (where you only need to disallow that one key pair).
Neither is the case in the scenario you described. If you were intending to use this in production then it would be a different matter but that doesn't appear to be the situation.
So it is far from OBVIOUS to me, having had proper academic schooling and some hands-on experience in information security.