Bug#492937: apt-setup: inconsistent path handling for 'security' and 'volatile' services

[Vincent McIntyre <Vince.McIntyre@atnf.csiro.au>]

package: debian-installer
severity: wishlist

Hi,

I was looking at packages/apt-setup/generators/and noticed a 
difference between the way that 91security and 92volatile add lines
to the new sources.list file (subversion, r54582):

 91security does this -
 echo "deb http://$host/ $codename/updates $dists" >> $file

 92volatile does this -
 echo "deb http://$host/debian-volatile $codename/volatile $dists" >> $file

I noticed this when I was trying to preseed these settings, but using
a local apt-proxy machine instead of security.d.o and volatile.d.o.

At present I can preseed the security source like this
  d-i apt-setup/security_host      string      aptproxy:9999/security
and the "right thing" happens.

But to get volatile right I would have to preseed differently
  d-i apt-setup/volatile_host      string      aptproxy:9999
and use the path /debian-volatile on the apt-proxy.

This would look a bit odd to an unitiated reader of the preseeding file.

To me, the answer appears to allow additional variables
  apt-proxy/security_path
  apt-proxy/volatile_path

and default these to '' and '/debian-volatile', respectively, so you
can do e.g.
  echo "deb http://$host/$path $codename/volatile $dists" >> $file

Then I could preseed the settings for my apt-proxy as well, in a nicer 
way.

Does this seem sensible? This might also help #364650.

Cheers
Vince