Merge branch 'cindex'

* cindex: (29 commits)
  cindex: --prune checkpoints to avoid OOM
  cindex: ignore SIGPIPE
  cindex: respect existing permissions
  cindex: squelch incompatible options
  cindex: implement reindex
  cindex: add support for --prune
  cindex: filter out non-existent git directories
  spawn: show failing directory for chdir failures
  cindex: improve granularity of quit checks
  cindex: attempt to give oldest commits lowest docids
  cindex: truncate or drop body for over-sized commits
  cindex: check for checkpoint before giant messages
  cindex: implement --max-size=SIZE
  sigfd: pass signal name rather than number to callback
  cindex: handle graceful shutdown by default
  cindex: drop `unchanged' progress message
  cindex: show shard number in progress message
  cindex: implement --exclude= like -clone
  ds: @post_loop_do replaces SetPostLoopCallback
  cindex: use DS and workqueues for parallelism
  ...

diff --cc lib/PublicInbox/IPC.pm
Simple merge

diff --cc lib/PublicInbox/LEI.pm
Simple merge