combine-diff: update --cc "uninteresting hunks" logic.
combine-diff: update --cc "uninteresting hunks" logic.

Earlier logic was discarding hunks that has difference from only
one parent or the same difference from all but one parent.  This
changes it to check if the differences on all lines are from the
same sets of parents.  This discards more uninteresting hunks
and seems to match expectations more naturally.

Signed-off-by: Junio C Hamano <dc50d1021234060e53ec42a77d526afa2fe07479@cox.net>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git