Yeah, just pushing both sides and hiding the merge bases -- all of them if there's more than one. From the rev-list docs:

```
Another special notation is "'<commit1>'...'<commit2>'" which is useful
for merges.  The resulting set of commits is the symmetric difference
between the two operands.  The following two commands are equivalent:

-----------------------------------------------------------------------
        $ git rev-list A B --not $(git merge-base --all A B)
        $ git rev-list A...B
-----------------------------------------------------------------------
```