Description of problem:

Upgrade path to dovecot in current devel tree broken.

dovecot: prockai
  5: 0:1.0-0.beta8.2.fc5 (FC5-updates)
  6: 0:1.0-0.beta8.2 (FC6)

I'd suggest making use of brew's newly added support for the %{?dist} tag, which
is widely used in Extras, like so:

RCS file: /cvs/dist/rpms/dovecot/devel/dovecot.spec,v
retrieving revision 1.52
diff -r1.52 dovecot.spec
4c4
< Release: 0.beta8.2
---
> Release: 0.beta8.2%{?dist}

That would make the next release in the devel tree 1.0-0.beta8.2.fc6, which is
sufficiently rpm-newer to repair the upgrade path.