Version control - can git implement some merge functions?

Question

I thought of such a scene

A project is divided into two parts A and B. A and B can basically be isolated from each other and have no other interactions

Now, for example, part A needs to be rewritten in other ways. Part A before the change is called A1, and after the change, it is called A2

A1 and A2 cannot be merged because they are written in completely different ways, but both A1 and A2 need to be retained

At this time, the project continues to develop backwards, and A1 and A2 are actually developed in parallel. How to deal with the development of B at this time?

Part B is needed after all

In addition to making A and B into two repos, is there any other way?

Answer 1

A1, A2 are two branches, and B is developed on the main line. Once there are changes in B, use git cherry-pick to merge the changes into A1, A2