This is very similar to edit_range_select_outside_rebase.go, except that it
selects commits right after, and including, a merge commit.
This test already works correctly. The reason we add it is that we are going to
have two different implementations of the `e` command depending on whether the
last selected commit is a merge commit, and we want to make sure they both work
with a range selection.
0b33634c73