TODO items for public-inbox

(Not in any particular order, and
performance, ease-of-setup, installation, maintainability, etc
all need to be considered for everything we introduce)

* general performance improvements, but without relying on
  XS or compiled code any more than we currently do.

* mailmap support (same as git) for remapping expired email addresses

* POP3 server, since some webmail providers support external POP3:
  https://public-inbox.org/meta/20160411034104.GA7817@dcvr.yhbt.net/
  Perhaps make this depend solely the NNTP server and work as a proxy.
  Meaning users can run this without needing a full copy of the
  archives in a git repository.

* HTTP and NNTP proxy support.  Allow us to be a frontend for
  firewalled off (or Tor-exclusive) instances.  The use case is
  for offering a publically accessible IP with a cheap VPS,
  yet storing large amounts of data on computers without a
  public IP behind a home Internet connection.

* optional Cache::FastMmap support so production deployments won't
  need Varnish (Varnish doesn't protect NNTP, either)

* dogfood and take advantage of new kernel APIs (while maintaining
  portability to older Linux, free BSDs and maybe Hurd).

* dogfood latest Xapian, Perl5, SQLite, git and various modules to
  ensure things continue working as they should (or more better)
  while retaining compatibility with old versions.

* Support more of RFC 3977 (NNTP)

* Combined "super server" for NNTP/HTTP/POP3 to reduce memory overhead

* Configurable linkification for per-inbox shorthands:
  "$gmane/123456" could be configured to expand to the
  appropriate link pointing to the gmane.org list archives,
  likewise "[Bug #123456]" could be configured to expand to
  point to some project's bug tracker at http://example.com/bug/123456

* configurable synonym and spelling support in Xapian

* Support optional "HTTPS Everywhere" for mapping old HTTP to HTTPS
  links if (and only if) the user wants to use HTTPS.  We may also
  be able to configure redirects for expired URLs.

  Note: message bodies rendered as HTML themselves must NOT change,
  the links should point to an anchor tag within the same page,
  instead; giving the user options.

* configurable constants (index limits, search results)

* handle messages with multiple Message-IDs (done for v2, doable for v1)

* handle broken double-bracketed References properly (maybe)
  and totally broken Message-IDs

  cf.  https://public-inbox.org/git/20160814012706.GA18784@starla/

* improve documentation

* linkify thread skeletons better
  https://public-inbox.org/git/6E3699DEA672430CAEA6DEFEDE6918F4@PhilipOakley/

* streaming Email::MIME replacement: currently we generate many
  allocations/strings for headers we never look at and slurp
  entire message bodies into memory.
  (this is pie-in-the-sky territory...)

* use REQUEST_URI properly for CGI / mod_perl2 compatibility
  with Message-IDs which include '%' (done?)

* 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.
  davfs2 needs Range: request support for this to be feasible:
    https://savannah.nongnu.org/bugs/?33259
    https://savannah.nongnu.org/support/?107649

* Contribute something like IMAP IDLE for "git fetch".
  Inboxes (and any git repos) can be kept up-to-date without
  relying on polling.

* Improve bundle support in git to make it cheaper to host/clone
  with dumb HTTP(S) servers.

* Expose targeted reindexing of individual messages.
  Sometimes an indexing bug only affects a handful of messages,
  so it's not worth the trouble of doing a full reindex.

* code repository integration (with cgit, gitweb, etc...)

* migration path to v2 without breaking v1 "git fetch" cronjobs

* imperfect scraper importers for obfuscated list archives
  (e.g. obfuscated Mailman stuff, Google Groups, etc...)

* support hooks, since low-level git-fast-import does not run them
  https://public-inbox.org/meta/20190405174329.GA21472@chatter.qube.local/
  (note: may not be needed since we do grokmirror manifest.js.gz, now)

* consider using HTTP::Date instead of Date::Parse, since we need the
  former is capable of parsing RFC822-ish dates, used by Plack, and
  the latter is missing from OpenBSD and maybe other distros.