folder and path completely broken in HEAD?

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

Hey, I'm playing around with the head of the git repository
(bc64cdce289d84be2550c4fccb1f008d15eaeb0e) to try to figure out how the
new folder: prefixes work, as folders are a critical part of how I
organize my mail.  (Since tags are not hierarchical, folders are the
best way for me to group mail to a bunch of related addresses, while
retaining the ability to separate out any mailboxes that become high
traffic.)

I'm using a pretty standard maildir++ layout.  For example, underneath
my database.path I have a bunch of mail in directories such as:

    .INBOX.Main/{new,cur}
    .mail.class/{new,cur}
    .mail.voicemail/{new,cur}

It used to be the case that if I wanted to read all of my "mail" mail, I
could search for folder:mail, while to look at just voicemail, I could
say folder:mail.voicemail, etc.  Now, I can't get anything to match a
folder predicate period.  For example, using notmuch as notmuch-0.17 and
./notmuch as notmuch-0.18-rc2+2~gbc64cdc, here's what I get:

        linux2$ notmuch count folder:mail
        16257
        linux3$ notmuch count folder:mail.class
        1896
        linux4$ notmuch count folder:mail.voicemail
        34
        linux5$ notmuch count folder:mail.voicemail/cur
        34
        linux6$ notmuch count folder:.mail.voicemail/cur
        34
        linux7$ ./notmuch count folder:mail
        0
        linux8$ ./notmuch count folder:.mail
        0
        linux9$ ./notmuch count folder:.mail.voicemail
        0
        linux10$ ./notmuch count folder:.mail.voicemail/cur
        0
        linux 11$ ./notmuch count path:.mail.voicemail
        0
        linux 12$ ./notmuch count path:.mail.voicemail/'**'
        0
        linux 13$ ./notmuch count path:.mail.voicemail/cur 
        0
        linux 14$ ./notmuch count folder:mail.voicemail
        0

What gives?  Are the path and folder predicates completely broken, or is
something very important missing from the new notmuch-search-terms
manual page?  How can I make this work?

Thanks,
David