This thing needs a regression test suite.

The grub linux-boot-probe has these limitations:

 - Does not handle grub present menus.
 - Does not support things like (hd0,1)/path/to/file
   although in the case of the kernel it will strip
   off the drive specification, and look for the file in the current
   partition.

The lilo linux-boot-probe has these limitations:

 - Doesn't map from devfs to normal if the lilo.conf uses devfs names
   (valid?)

linux-boot-prober:

- Partition names in boot loader config may have changed during
  the debian install, so cannot be trusted. Fix up root= lines,
  etc.
- To get to boot/, may need to parse fstab. But this can fail because
  as noted above, drive names may have changed!
- Maybe do some probing before partitioning and store info?
  Or don't support adding partitions before existing /boot partitions.