[PATCH] lib: update cached mtime in notmuch_directory_set_mtime

[David Bremner]

David Bremner <david at tethera.net> writes:

> Without this change, the following code fails
>
>   notmuch_directory_set_mtime(dir, 12345);
>   assert(notmuch_directory_get_mtime(dir) == 12345);

pushed.

Hopefully nobody relied on the old, weird, behaviour.

d