There's a lot of weird code in public-inbox which may be daunting
to new hackers.

* The event loop (PublicInbox::DS) is an evolution of a fairly standard
  C10K event loop.  See ds.txt in this directory for more.

Things got weirder in 2021:

* The lei command-line tool is backed by a daemon.  This was done to
  improve startup time for shell completion and manage git/SQLite/Xapian
  single-writer during long, parallel imports.  It may eventually become
  a read-write IMAP/JMAP server.

* SOCK_SEQPACKET is used extensively in lei, and will likely make its
  way into more places, still.

And even more so in 2022:

* public-inbox-clone / PublicInbox::LeiMirror relies on ->DESTROY
  for make-like dependency management while providing parallelism.

More to come, lei will expose Maildirs via FUSE 3...
