 
Magit offers a means of invoking Ediff to resolve a merge conflict via the e binding from the magit-status ((magit) Status Buffer) window.
Calling casual-ediff-tmenu will show the menu shown above. Note that in the C section, there are commands to merge both the variant A and variant B diffs using the bindings mab or mba, depending on the desired order the diffs are to be merged.