+ as well as:
+
+ "tag:notmuch and <date-range>" SET-INTERSECT
+ "tag:notmuch and not (tag:merged or tag:postponed)"
+
+ See id:3wdpr282yz2.fsf@testarossa.amd.com for more details on the
+ use cases of the above.
+
+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).
+
+Add support for the user to specify custom headers to be indexed (and
+re-index these for existing messages at the next database upgrade).
+
+Save filenames for files detected as "not an email file" in the
+database. This would allow for two things: 1. Optimizing "notmuch new"
+to not have to look at these files again (since they are potentially
+large so the detection could be potentially slow). 2. A "notmuch
+search" syntax could be added to allow the user to find these files,
+(and perhaps delete them or move them away as appropriate).
+
+Fix filesystem/notmuch-new race condition by not updating database
+mtime for a directory if it is the same as the current mtime.
+
+Test suite
+----------
+Achieve 100% test coverage with the test suite.