Was tendermint/tendermint#9002

Summary

p2p message format for BlockSync messages are out of date for (future) v0.38.x and main branches

Problem Definition

Since the introduction of vote extensions (part of ABCI++) the BlockSync messages (optionally) contain the extended commit corresponding to the the block contained in the p2p blocksync message.

We need to update the p2p spec, in particular, this.