On 29.1.2011, at 2.38, Rob Browning wrote:

In this particular case, we're thinking of trying to allow notmuch to operate directly on the dovecot Maildir, and at the moment, the only modifications notmuch makes are to change maildir flags. Would locking dovecot-uidlist.lock be sufficient, perhaps via liblockfile?

If you're only changing the standard maildir flags (not a..z = keywords) then you don't really need to lock anything. The uidlist locking could prevent a mail from being temporarily lost, but this happening is highly unlikely. http://wiki2.dovecot.org/MailboxFormat/Maildir#Locking explains.

Also, is there some reliable way to detect a dovecot Maildir? For example, are any of the dovecot-* files guaranteed to exist all the time?

dovecot-uidlist always exists, but in some installations it's stored outside the maildir.