Currently most everything a pipeline reference can be stored in a git except 2 things.
Variables and Overrides V2.
I see there is already an RFE for overrides v2 to be backended by git.
RFE to allow variables to be stored in git.
Now that services are allowed to be stored in git, the variables associated with service are in git. Would request to keep this user experience across the board where variables are first class git citizens