-Fix "notmuch restore" to delete the old tags from a message/thread
-before adding new ones. This will require someway to temporarily
-'disconnect' a notmuch_message_t from the database, (that it, disable
-automatic sync for add_tag, etc.), and then reconnect it. That is, the
-removal and subsequent addition of tags to the message/thread needs to
-be transactional.
+Audit everything for dealing with out-of-memory (and drop xutil.c).
+
+Write a test suite.
+
+Achieve 100% test coverage with the test suite.