The commit added another parameter so it is possible to skip the expensive get_all_keys call. It is defaulted to true so that old code that called get_bucket()

The commit added another parameter so it is possible to skip the expensive get_all_keys call. It is defaulted to true so that old code that called get_bucket() won't break. (Since old code would have used get_bucket with only one parameter.) It was always true before that commit. Therefore, in essence, an Amazon employee made it possible to save 90% of your S3 bills.