git-cherry and fork-point

Hello

I'd like to understand what's the 'fork-point' in the git-cherry documentation.

For example, if I have this configuration:

                                 __*__*__*__*__> <upstream>
                                /
                 *__A__*__*__*__B__*
                     \
                      \__+__+__-__+__+__-__+__> <head>

what's the 'fork-point' for respectively those two commands:

       $ git cherry upstream head B
       $ git cherry head upstream A

I would say A and B, but I'm not sure and the documentation doesn't help.

Could anybody clarify this point ?

Thanks