Jeff King wrote:

  [1/2]: usage: allow pluggable die-recursion checks
  [2/2]: run-command: use thread-aware die_is_recursing routine

Lovely.  This doesn't solve the analagous problem for grep,
index-pack, pack-objects, preload-index, or bidirectional_transfer_loop,
but it doesn't make them worse and even should make them easier to fix
later, so

Reviewed-by: Jonathan Nieder <redacted>