Causally sort a collection of messages.
Returns messages sorted from newest to oldest.
If message b includes a reference to message a then we say that message b must have been
published after message a, assuming these assumptions hold:
- The hash function is not broken (Two different sets of bytes return the same hash.)
- The person publishing
message bhas not guessed a valid hash of a message before it was published (extremely unlikely.) - The person publishing
message bis not a time traveller.
This function uses daggy to build a dag of references between messages and then topologically sorts them.
If a message is not referenced by any messages you can expect it to be sorted to the start of the results (it is so new no one has referenced it yet).