[Dovecot] INBOX of a shared namespace appears to be always subscribed

[Holger Richter]

In dovecot 1.2.10 I run into the following problem: Our users are  
entitled to share their personal mailboxes. This works. But if user A  
shares any of its mailboxes with user B, then dovecot always reports  
the INBOX of user A as subscribed by user B. No matter whether user B  
really subscribed the INBOX of A, or whether user A permitted user B  
the access to its INBOX. The problem is caused by the repeated call of  
LSUB. Starting with the second call LSUB always shows INBOX as  
subscribed.

To reproduce:
-> telnet imap.xx.yy 143
          1 LOGIN user password
          2 LSUB "" shared/*    => shows shared/UserB/folderXX
          3 LSUB "" shared/*    => shows shared/UserB/INBOX
                                         shared/UserB/folderXX
          4 LSUB "" shared/*    => shows shared/UserB/INBOX
                                         shared/UserB/folderXX
Regards, Holger