message-id support

[donpdonp]

I'd like to have my irc bot listen with two connections to the network for redundancy/reliability. It would need to de-duplicate messages and that means a unique ID per message generated at the client ideally, or at the server. If ircd-seven is a fork of charybdis, the NEWS file says charybdis got message tags 2 years ago yet none of that code appears to be in irc-seven. when is the last time ircd-seven merged new code from charybdis?

the notes for charybdis 4, released March 2016, list support for IRCv3 message tags.
https://github.com/charybdis-ircd/charybdis/blob/master/NEWS.md

[ilbelkyr]

This depends on us implementing support for message tags, as tracked in #170.