Bug#959712: Add probe module to signed UEFI images

[Alkis Georgopoulos]

Package: grub2
Version: 2.04-7
Severity: wishlist

I would like to boot debian.iso directly from grub, e.g. from a live USB 
stick: https://github.com/alkisg/liveusb

For Debian, this requires to pass the following cmdline to the kernel:
fromiso=/dev/disk/by-uuid/$rootuuid/$iso boot=live

In order to "translate" grub's $root (e.g. hd0,msdos1) into kernel's 
$rootuuid (e.g. 1234-5678), the probe command is needed:
probe --set=rootuuid --fs-uuid "$root"

It's a very small module, please consider including it to signed images 
similar to this patch for the regexp module:

https://salsa.debian.org/grub-team/grub/commit/07481aa3deecc58247525d4e69f1f4f7ffbefe33

Thank you!