This is a different but related issue to issue1966

It ought to be possible to have a repository-global version of 
_darcs/prefs/{email,motd}, which at the moment is local only to the 
current repository.

The two key differences with the existing _darcs/prefs version are that 
(a) it can travel via get/pull/push/etc and (b) you can version control 
it.  You could also conceivably implement a weaker version that only 
does a bit of (a), say only travels on darcs get time, but I think that 
weaker version would just be complicating the UI for nothing.  If we're 
going to complicate matters, at least do it right.

I think at least Trent has made this observation before, but I can't 
find the ticket.

If there is a local _darcs/{prefs,email}, it should override the repo-
wide one.

Note that the related issue1966 talks about the UI for controlling such 
preferences should they become possible.  This ticket is for just 
implementing the idea of things like email/motd being repo-global.