Shorthand for "$(git merge-base A B)"

I find myself fairly frequently doing something like "git log $(git merge-base A B)..C". As far as I can tell, there is no shorthand for the $() part of this, but it seems like something that could be pretty naturally added, or documented better if there is some esoteric combination of the existing shorthands that would support it.

Is there any way to support a shorthand for $(git merge-base A B)? I hoped a joiner in the spirit of A..B could be used:

A::B A*B A%B If not, maybe A@{mb:B} or something along those lines?

I can imagine this would be a non-trivial amount of work, just wondering if there is interest, or if anybody has thoughts on the notation?

Thanks, John