+* more and better test cases (use git fast-import to speed up creation)
+
+* large mbox/Maildir/MH/NNTP spool import (see PublicInbox::Import)
+
+* Read-only WebDAV interface to the git repo so it can be mounted
+ via davfs2 or fusedav to avoid full clones.
+
+* Improve tree layout to help giant archives (v2 format):
+
+ * Must be optional; old ssoma users may continue using v1
+
+ * Xapian becomes becomes a requirement when using v2; they
+ claim good scalability: https://xapian.org/docs/scalability.html
+
+ * Allow git to perform better deltafication for quoted messages
+
+ * Changing tree layout for deltafication means we need to handle
+ deletes for spam differently than we do now.
+
+ * Deal with duplicate Message-IDs (web UI, at least, not sure about NNTP)
+
+ * (Maybe) SQLite alternatives (MySQL/MariaDB/Pg) for NNTP article
+ number mapping: https://www.sqlite.org/whentouse.html
+
+ * Ref rotation (splitting heads by YYYY or YYYY-MM)