If 'tags' is already pointing at the last tag then the iterator
will be moved to a point just beyond that last tag, (where
notmuch_tags_valid will return FALSE and notmuch_tags_get will
return NULL).
See the documentation of notmuch_message_get_tags for example code
showing how to iterate over a notmuch_tags_t object.
Move the 'tags' iterator to the next tag.
If 'tags' is already pointing at the last tag then the iterator will be moved to a point just beyond that last tag, (where notmuch_tags_valid will return FALSE and notmuch_tags_get will return NULL).
See the documentation of notmuch_message_get_tags for example code showing how to iterate over a notmuch_tags_t object.