I was trying to figure out why, using my new Dovecot install, I was not
getting UIDPLUS or QRESYNC capabilities.  I found out that it was
because the capabilities were determined at connection time, and the set
of advertised capabilities changes between connection and login.  Upon
login on Dovecot, an updated set of capabilities may be advertised.  I
was able to account for that using the included patch.  A perhaps-better
method might be to re-run CAPABILITY after logging in.