[Dovecot] dovecot 2.1 breaks FTS + pre-auth?

[dm-list-email-dovecot at scs.stanford.edu]

Hi.  I use dovecot in the simplest possible way, as an IMAP server in
pre-auth mode over ssh or just locally over a unix-domain socket
(e.g., with offlineimap, which runs much faster using dovecot for the
local message store).  Ideally I would like to avoid running any extra
daemons or setting up anything as root.  Until recently, this has
worked fine by just setting the CONFIG_FILE environment variable to
something in my home directory.

Here is my configuration:

$ export CONFIG_FILE=$HOME/etc/dovecot.conf
$ dovecot -n
# 2.1.3: /home/dm/etc/dovecot.conf
# OS: Linux 3.2.13-1-ARCH x86_64  
mail_location = maildir:~/Mail/inbox
mail_plugins = " fts fts_squat"
plugin {
  fts = squat
  fts_squat = partial=4 full=10
}
doveconf: Error: ssl enabled, but ssl_cert not set
doveconf: Fatal: Error in configuration file /home/dm/etc/dovecot.conf: ssl enabled, but ssl_cert not set

Full text search used to work just fine with this configuration, and
still does on a machine I have running dovecot 2.0.13.  However, on
the machine with 2.1, I get errors about /var/run/dovecot/index not
existing.

$ printf "a select INBOX\nb search text xyzzy\nc logout\n" \
    | /usr/lib/dovecot/imap
* PREAUTH [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE SORT SORT=DISPLAY THREAD=REFERENCES THREAD=REFS MULTIAPPEND UNSELECT CHILDREN NAMESPACE UIDPLUS LIST-EXTENDED I18NLEVEL=1 CONDSTORE QRESYNC ESEARCH ESORT SEARCHRES WITHIN CONTEXT=SEARCH LIST-STATUS SPECIAL-USE] Logged in as dm
imap(dm): Error: net_connect_unix(/var/run/dovecot/indexer) failed: No such file or directory
...

Needless to say, no dovecot.index.search or dovecot.index.search.uids
file is created after this error.

While I can't write /var/run/dovecot, this is not a permission issue.
For example, adding base_dir=/home/dm (my home directory) to the
configuration file yields the same error for /home/dm/indexer.  I'm
guessing something has changed where imap requires an indexer daemon
and doesn't launch it in pre-auth mode any more, but I can't find
anything about this in the documentation.

In short, if anyone can tell me how to use FTS in conjunction with
pre-auth mode or point me to a working example, I would appreciate it.