Confused about project2B's impl peer storage "PeerStorage.SaveReadyState" description

[BaymaxHWY]

The original description is "To append log entries, simply save all log entries at raft.Ready.Entries to raftdb and delete any previously appended log entries which will never be committed. Also, update the peer storage’s RaftLocalState and save it to raftdb."

what log is "delete any previously appended log entries which will never be committed" ?
I looked at previous implementations of TIKV, the deleted log entries is the index between in [raft.Ready.Entries first index , the peer.raftState.LastIndex], why delete these ? writes to the new entries should override the original log, maybe just delete the log which index between in [raft.Ready.Entries last index, the peer.raftState.LastIndex]

[BaymaxHWY]

I'm blind，your impl is delete the log which index between in [raft.Ready.Entries last index, the peer.raftState.LastIndex], sorry, but I would suggest that this logical description be a little bit more detailed, right?