Performing a 4 way diff with ediff

[Dan LaManna]

Hi all,

I've been using ediff to resolve merge conflicts in git and it has the
typical windows: ours, theirs, and merged results. However, I often want
to see a 4th window (I believe this is called a 4 way diff) which is the
common ancestor of ours and theirs (A and B). I believe such
functionality exists in vimdiff - is there an ediff (or other emacs
tool) offering similar functionality to this?

Thanks, 

Dan