Merge pull request #700 from cholin/revwalk_reset

really reset walker with git_revwalk_reset

src/revwalk.c

@@ -838,5 +838,8 @@ void git_revwalk_reset(git_revwalk *walk)
 	commit_list_free(&walk->iterator_rand);
 	commit_list_free(&walk->iterator_reverse);
 	walk->walking = 0;
+
+	walk->one = NULL;
+	git_vector_clear(&walk->twos);
 }