Use FetchDirectoryContents for filtering instead of the SearchDirectory
message. This was an omission from rebasing the mbox worker and from not
realizing that c2f4404f ("threading: enable filtering of server-side
threads") changed the way we filter in the message store for the
server-side threading implementation. This patch enables filtering for
the mbox worker.
Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>