In a git merge, how do you just replace your version with the version git says there is a conflict with?

I have two files: A and B. If I have been working on A and a partner is working on B, I want to merge files A and B. B is already committed. Let's say my partner already made the changes I was working on, so I just want to replace my A file with their B file - no merge needed. How do I resolve the conflict with git?

Thanks!