Add documentation for sorting constants.
Add documentation for sorting constants.

libgit2/rugged,tpickett66/rugged,libgit2/rugged,saraid/rugged,tpickett66/rugged,saraid/rugged,saraid/rugged,Acidburn0zzz/rugged,libgit2/rugged,tpickett66/rugged,Acidburn0zzz/rugged,Acidburn0zzz/rugged