+ (done for most git blob retrievals, Xapian needs work)
+
+* HTTP(S) search API (likely JMAP, but GraphQL could be an option)
+ It should support git-specific prefixes (dfpre:, dfpost:, dfn:, etc)
+ as extensions. If JMAP, it should have HTTP(S) analogues to
+ various IMAP extensions.
+
+* search across multiple inboxes, or admin-definable groups of inboxes
+
+ This will require a new detached Xapian index that can be used in
+ parallel with existing per-inbox indices. Using ->add_database
+ with hundreds of shards is unusable in current Xapian as of
+ August 2020 (acknowledged by Xapian upstream).
+
+* scalability to tens/hundreds of thousands of inboxes
+
+ - pagination for WwwListing
+
+ - inotify-based manifest.js.gz updates
+
+ - process/FD reduction (needs to be slow-storage friendly)
+
+ ...
+
+* command-line tool (similar to mairix/notmuch, but solver+git-aware)
+
+* consider removing doc_data from Xapian, redundant with over.sqlite3
+ It's no longer read as of public-inbox 1.6.0, but still written for
+ compatibility.
+
+* share "git cat-file --batch" processes across inboxes to avoid
+ bumping into /proc/sys/fs/pipe-user-pages-* limits
+
+* make "git cat-file --batch" detect unlinked packfiles so we don't
+ have to restart processes (very long-term)
+
+* support searching based on `git-patch-id --stable` to improve
+ bidirectional mapping of commits <=> emails
+
+* linter to check validity of config file
+
+* linter option and WWW endpoint to graph relationships and flows
+ between inboxes, addresses, Maildirs, coderepos, newsgroups,
+ IMAP mailboxes, etc...
+
+* pygments support - via Python script similar to `git cat-file --batch'
+ to avoid startup penalty. pygments.rb (Ruby) can be inspiration, too.
+
+* highlighting + linkification for "git format-patch --interdiff" output
+
+* highlighting for "git format-patch --range-diff" output
+ (linkification is too expensive, as it requires mirroring)
+
+* support UUCP addresses for legacy archives