Improve the readability of the code

[zhixunjie]

Whether it is necessary to put such a large section of the annotation into the code, I think it is not necessary, because it greatly affects the readability of the code. I suggest finding a document to collect these annotations uniformly, and then only need to refer to the location of these documents in the code.

[jmhbnz]

Hi @zhixunjie - Thanks for raising this idea. Can you please be more specific about which comments/annotation in the code you think are not necessary or should be moved elsewhere?

[zhixunjie]

like this large section（about 90+ lines）：

etcd/raft/raft.go

Line 1127 in 0223ca5

if m.LogTerm > 0 {

when i tried to figure out the mechanism about how to deal with the follower's reject here，it made me so confused；