+/* Create a new notmuch_message_t object for an existing document in
+ * the database.
+ *
+ * Here, 'talloc owner' is an optional talloc context to which the new
+ * message will belong. This allows for the caller to not bother
+ * calling notmuch_message_destroy on the message, and no that all
+ * memory will be reclaimed with 'talloc_owner' is free. The caller
+ * still can call notmuch_message_destroy when finished with the
+ * message if desired.
+ *
+ * The 'talloc_owner' argument can also be NULL, in which case the
+ * caller *is* responsible for calling notmuch_message_destroy.
+ *
+ * If no document exists in the database with document ID of 'doc_id'
+ * then this function returns NULL.
+ */