GRUB2 does not migrate Legay's 40_custom correctly

[YannUbuntu]

Dear GRUB devs, here is a little bug that could be easily fixed:

1) Initial situation: A pc with Linpus OS (uses GRUB Legacy).

2) Then installed Ubuntu 9.04 , which added Linpus in its GRUB Legacy 's 40_custom correctly, as:
title Linpus Linux RCD (on /dev/sda1)
root (hd0,0)
kernel /boot/bzImage ro root=LABEL=linpus vga=0x311 splash=silent loglevel=1 console=tty1 quiet nolapic_timer
initrd /boot/initrd-splash.img
savedefault
boot

3) Then added Ubuntu 11.10. Its os-prober does not detect Linpus. Its GRUB2 migrated the 40_custom Linpus entry from Legacy as:
title Linpus Linux RCD (on /dev/sda1)
root (hd0,0)
kernel /boot/bzImage ro root=LABEL=linpus vga=0x311 splash=silent loglevel=1 console=tty1 quiet nolapic_timer
initrd /boot/initrd-splash.img
savedefault
boot

Result: GRUB2 menu didn't allow boot on Linpus.

Expected result: GRUB2 should have increased +1 the partition number: (hd0,1) instead of (hd0,0). (bug and solution confirmed by a French user: http://forum.ubuntu-fr.org/viewtopic.php?pid=7760671#p7760671 )

[Phillip Susi (psusi)]

Grub legacy did not have /etc/grub.d and 40_custom is for you to manually edit; it's contents are not generated automatically.