We prior required they had the same encoding, yet this ensures they do by
making them one and the same. This does require an large, ugly, From/TryInto
block which is deemed preferable for moving this more and more into syntax
(from semantics).
Further improvements (notably re: Extra) is possible, and this already lets us
strip some members from the Call enum.
* Rewrite tendermint's message handling loop to much more clearly match the paper
No longer checks relevant branches upon messages, yet all branches upon any
state change. This is slower, yet easier to review and likely without one or
two rare edge cases.
When reviewing, please see page 5 of https://arxiv.org/pdf/1807.04938.pdf.
Lines from the specified algorithm can be found in the code by searching for
"// L".
* Sane rebroadcasting of consensus messages
Instead of broadcasting the last n messages on the Tributary side of things, we
now have the machine rebroadcast the message tape for the current block.
* Only rebroadcast messages which didn't error in some way
* Only rebroadcast our own messages for tendermint
Instead of saving, for every sent message, if it was sent or not, we track the
latest block/round participated in. These two keys are comprehensive to all
prior block/rounds. We then use three keys for the latest round's
proposal/prevote/precommit, enabling tracking current state as necessary to
prevent equivocations with just 5 keys.
The storage of the latest three messages also enables proper rebroadcasting of
the current round (not implemented in this commit).
Online validators should inherently have them. Offline validators will receive
from the sync protocol.
This does somewhat eliminate the class of nodes who would follow the blockchain
(without validating it), yet that's fine for the performance benefit.
