How to work with different versions of the same project?

Question

git

Hello.
I have a Visual Studio project on the basis of which I am currently making another one. Minor changes in connections to databases, structures, somewhere buttons need to be changed, and so on. But while working on this second project, I sometimes make changes that would be nice to make on the first one. At the moment, I copy what I need with pens into the main project. I suspect that someday I will forget to add something or something.
What is the best way to work with projects in this case?
Thank you.

Answer 1

Create a 3rd project and put common files there. And in the first two projects, add these files with the link "Add as Link"