on push to submodule:
  error on non-fast-forward
  error on pushing tag
  zephyr

superrepo heads are dev and prod
on push to superrepo:
  error - no pushes to superrepo

on remctl xvm repo (dev|prod) package SHA-1:
  use remctl ACLs to limit pushes to correct groups
  verify that new version number is greater than previous
  echo "(dev|prod) package SHA-1" > $build_queue/TIMESTAMP

while build queue is not empty:
  find min(os.listdir($build_queue))
  (as optimization: if same commit already in dev, just reprepro move)
  try to build submodule
    if fail:
      keep build around
      send mail with log
      zephyr
  upload to apt repo
  tag submodule with version
  commit superrepo with updated submodule
  clean up build files
  zephyr
  rm $build_queue file