Why am I given three choices when merging between my code and someone else's? Shouldn't there just be my code, the other person's code, and the output below? The documentation for KDIFF doesn't help me understand.
Sounds like you're doing a three-way merge, so A should be the base revision that B and C are based on, B is theirs and C is yours (I believe; B and C might be the opposite, though).