+Transition `notmuch_database_add_message` to `notmuch_database_index_file`
+
+ When indexing an e-mail message, the new
+ `notmuch_database_index_file` function is the preferred form, and
+ the old `notmuch_database_add_message` is deprecated. The new form
+ allows passing a set of options to the indexing engine, which the
+ operator may decide to change from message to message.
+