+Database changes
+----------------
+Store a reference term for every message-id that appears in
+References. We just started doing this for newly-added documents, but
+at the next convenient database-schema upgrade, we should go back and
+fix old messages to be consistent.
+
+Start indexing the List-Id header, (and re-index this header for
+existing messages at the next database upgrade).
+
+Start indexing the message file's directory and make it available for
+search as "folder:" (and re-index this value for existing messages at
+the next database upgrade).
+
+Add support for the user to specify custom headers to be indexed (and
+re-index these for existing messages at the next database upgrade).
+
+Test suite
+----------
+Achieve 100% test coverage with the test suite.
+
+General
+-------
+Audit everything for dealing with out-of-memory (and drop xutil.c).
+
+Investigate why the notmuch database is slightly larger than the sup
+database for the same corpus of email.