[Dovecot] dsync mirror duplicates problem

[Timo Sirainen]

On Sat, 2010-08-28 at 17:58 +0200, Waldemar W. wrote:
> Problem occurs when mails arrive in the same folder on both sides then 
> dsync sometimes runs into problems
> and duplicates that entrys on both side(2mails then with same 
> content). After running again
> the same happens again(now 4 mails with same content on every side). 
> And then duplicates this mails on
> both sides on every run :(
> Anyone with same problem or is something that could cause this? I 
> tried dsync with and without -f option but no change.

Oh, right.. The old conflict resolution method worked only with Maildir.
The new conflict resolution method works with everything except
Maildir. 

The problem is that the new method works by first copying the message to
give it a new UID but preserve its GUID, and then expunging the old one.
But with Maildir the message filename is the GUID, so it's not possible
to have two messages in the same mailbox with the same GUID. So Dovecot
gives a new filename/GUID to the copied message, which dsync next time
thinks is conflicting and tries to resolve it, and then this continues
forever..

Hmm.. I guess one solution to this would be to allow overriding the
filename as GUID in dovecot-uidlist.. Or I can't really even think of
any other solution. Hopefully won't be too horribly difficult to
implement it.