Moves logic for creating dynamic folders from the dirlist widget to the
backend. Since dynamic folders are notmuch-specific, the notmuch backend
should be responsible for correctly setting up those folders. It does
that by sending two DirectoryInfos: the first to create the message
store, the second to fetch the directory content.
This approach also fixes a deadlock introduced by 716ade8968
("worker: lock access to callback maps").
Reported-by: Bence Ferdinandy <bence@ferdinandy.com>
Signed-off-by: Koni Marti <koni.marti@gmail.com>
Tested-by: Tim Culverhouse <tim@timculverhouse.com>
0e50f29bf3