[preseed] multiple disks, rules to select the "smallest" one

[Sandro Tosi <morph@debian.org>]

Hello,
in case a machine has just one disk, we can skip the

    d-i partman-auto/disk string <device>

line and the d-i will do the right thing.

Sometimes we also have machines with multiple drives, consider the now
usual case of a fast SSD for the OS and a slower/larger spinning drive
for data.

In order to avoid writing a custom preseed file all the times, we're
wondering if there is already a policy that would instruct d-i to use
the smallest physical drive on the system as the one to partition and
use for installation or alternatively how we should write our
preseed.cfg to obtain that (eventually with some early_command?).

Thanks in advance for your help,
-- 
Sandro Tosi (aka morph, morpheus, matrixhasu)
My website: http://matrixhasu.altervista.org/
Me at Debian: http://wiki.debian.org/SandroTosi