notmuch_database_find_message_by_filename does exactly what it says.
+API changes
+
+ notmuch_database_find_message (and n_d_f_m_by_filename) now return
+ a status indicator and uses an output parameter for the
+ message. This change required changing the SONAME of libnotmuch to
+ libnotmuch.so.2
+
Python bindings changes
-----------------------