While true, using someone else's trademark as a prefix of your name when you are actively intending it to reference the protected use seems egregious.

Do you think many users will mistakenly believe Gitlip is an official Git project put out by the same authors as Git?

There can't be trademark infringement unless there is a likelihood of confusion.

I don't know. I do know that an incredible number of users do not understand that GitHub is NOT an official anything, and so I feel like we have an existence proof of this being a serious concern. (That said, I also can see an argument that once git allowed that to happen without a fight, or even AFAIK at least some retroactive agreement--and then further also allowed GitLab--that they don't even have an enforceable trademark anymore, at least with respect to this kind of prefix use. But like, this is a kind of oblique argument that I don't think you are already making.)