simplemerge: make merge_groups() yield only 2-tuples...
simplemerge: make merge_groups() yield only 2-tuples
`merge_groups()` currently yields 2-tuples or 4-tuples, making the
callers check the first element to decide how to interpret the
rest. Let's make it yield only 2-tuples, thereby simplifying life a
little for the callers.
Differential Revision:
https://phab.mercurial-scm.org/D11966
