merge-recursive: Avoid excessive output for and reprocessing of renames

In 5a2580d (merge_recursive: Fix renames across paths below D/F conflicts 2010-07-09) and ae74548 (merge-recursive: Fix multiple file rename across D/F conflict 2010-08-17), renames across D/F conflicts were fixed by making process_renames() consider as unprocessed renames whose dst_entry "still" had higher stage entries. The assumption was that those higher stage entries would have been cleared out of dst_entry by that point in cases where the conflict could be resolved (normal renames with no D/F conflicts). That is not the case -- higher stage entries will remain in all cases. Fix this by checking for higher stage entries corresponding to D/F conflicts, namely that stages 2 and 3 have exactly one nonzero mode between them. The nonzero mode stage corresponds to a file at the path, while the stage with a zero mode will correspond to a directory at that path (since rename/delete conflicts will have already been handled before this codepath is reached.) Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>