merge: introduce 'commitinfo' in mergeresult commitinfo will be used to pass information which is required on commit phase from the merge phase. One common example is, merge chooses filenode from second parent and we need to tell commit to choose that. Right now this one and related cases are not very neatly implement and there is no clear line on how to pass on such information. Upcoming patches will try to work on in this area and make things easier. Differential Revision: https://phab.mercurial-scm.org/D8742