When I get into a three-way merge there tends to be a lot of visual clutter. Here’s a screenshot from the merge I’m doing right now:
In this case after a very careful reading I understand that the what’s happened here is that I changed the name of the method on the right side and its implementation on the left. I’m pretty sure that’s correct at least.
My point is that I shouldn’t have to eyeball it, and I should be more than pretty sure. There’s no simpler way to gain all the context on a three way merge than being able to see each set of changes compared to the base.
It’s also useful to be able to do a two-way comparison where one side is the merge result. The other side may be the base (currently unsupported), the left side (currently 3-way view does this), or the right side (which three way view does sort of show but not with highlighting of differences within lines).
If it is useful as a reference, IntelliJ offers similar functionality, which is where I learned how useful it can be.