Just out of curiosity, do we need to backport changes to stuff in /packages? There is no useful way to match up the npm versions with the Kibana branches anyway.

Hmm... the way I'm looking at it is, if I check out a branch, I'd expect that branch to have a logical commit history and a consistent internal state. So, I'd find it a little strange if I know that we store the source for a dependency within the repo, yet that dependency's source is several versions behind the version we depend upon. It can seem like a mistake to someone who's reading the code. For that person to understand what's really going on, they'd need to check out another branch or poke around on GitHub. IMO, we should treat branches as self-contained units, so this kind of external exploration doesn't become necessary to understand the code.