[Dovecot] Deliver autocreate with auto-subscribe?

[Paul Reilly]

Hello,

I'm using dovecot with postfix configured for address extensions, so
email to me+folder at mydomain.com <me%2Bfolder at mydomain.com>, automatically is
handed off
to dovecot deliver, which sees there is no folder called "folder"
and autocreates it. This is brilliant, as it means I can give out
subject orrientated email addresses, and the mail is automatically
put in the right mailbox :)  I love dovecot with postfix.

However, my problem is my IMAP client (roundcube and HordeIMP) does
not see the newly created folder. I have to manually subscribe it in
the webmail client, or I have to add the folder to the "subscriptions"
file in my home dir. So my question is, can the deliver command
which auto-creates this folder, also add it to the subscriptions file?
It seems like it just needs another switch on the command line.
http://wiki.dovecot.org/LDA

Is this currently possible, and if not, what code do I need to hack
to make it work?

Thanks
Paul