Bug#273212: Problem using apt with an alternate configuration

[Sébastien GALLET <sgallet@ibourgogne.net>]

Package: apt
Version: 0.5.27

I want to use apt with an alternate configuration. 
But it seems apt use configuration from /etc/apt/apt.conf.d, 
not the one of the alternate configuration

How to reproduce the bug :
mkdir -p /etc/kpt/apt.conf.d
cp /etc/apt/sources.list /etc/kpt/

/etc/kpt/apt.conf :
APT
{
 Architecture "i386";
 Clean-Installed "true";
 Default-Release "sarge";

 Get
 {
    Show-Upgraded "true";
    Show-Versions "true";
    Assume-Yes "true";
    Fix-Missing "true";
    Fix-Broken "true";
    List-Cleanup "true";
    Purge "false";
 };
};

Dir
{
 Etc "etc/kpt/";
 State "var/lib/kpt/";
 Cache "var/cache/kpt/";
};

KPT
{
 Kernel
 {
    Arch "k7-mem4";
    Version "2.4.27";
 };
};

/etc/kpt/apt.conf.d/10-install :

DPkg
{
Post-Invoke {"/usr/bin/kpt-install-kernel";};
};

Now when i run apt-config :
#apt-config -c=/etc/kpt/apt.conf dump
-------------------- THIS PART IS OK. IT COMES FROM /etc/kpt
APT "";
APT::Architecture "i386";
APT::Build-Essential "";
APT::Build-Essential:: "build-essential";
APT::Get "";
APT::Get::Assume-Yes "true";
APT::Get::Fix-Missing "true";
APT::Get::Show-Upgraded "true";
APT::Get::Purge "false";
APT::Get::List-Cleanup "true";
APT::Get::ReInstall "false";
APT::Get::Show-Versions "true";
APT::Get::Fix-Broken "true";
APT::Clean-Installed "true";
APT::Default-Release "sarge";
Dir "/";
Dir::State "var/lib/kpt/";
Dir::State::lists "lists/";
Dir::State::cdroms "cdroms.list";
Dir::State::userstatus "status.user";
Dir::State::status "/var/lib/dpkg/status";
Dir::Cache "var/cache/kpt/";
Dir::Cache::archives "archives/";
Dir::Cache::srcpkgcache "srcpkgcache.bin";
Dir::Cache::pkgcache "pkgcache.bin";
Dir::Etc "etc/kpt/";
Dir::Etc::sourcelist "sources.list";
Dir::Etc::vendorlist "vendors.list";
Dir::Etc::vendorparts "vendors.list.d";
Dir::Etc::main "apt.conf";
Dir::Etc::parts "apt.conf.d";
Dir::Etc::preferences "preferences";
Dir::Bin "";
Dir::Bin::methods "/usr/lib/apt/methods";
Dir::Bin::dpkg "/usr/bin/dpkg";
-------------------- THIS PART IS NOT OK. IT COMES FROM /etc/apt/apt.conf.d/
DPkg "";
DPkg::Pre-Install-Pkgs "";
DPkg::Pre-Install-Pkgs:: "/usr/sbin/dpkg-preconfigure --apt || true";
DPkg::Post-Invoke "";
DPkg::Post-Invoke:: "if [ -x /usr/sbin/localepurge ] && [ $(ps w -p $PPID | grep -c remove) != 1 ]; then /usr/sbin/localepurge; else exit 0; fi";
DPkg::Options "";
DPkg::Options:: "--abort-after=4711";
-------------------- THIS PART IS OK. IT COMES FROM /etc/kpt
KPT "";
KPT::Kernel "";
KPT::Kernel::Arch "k7-mem4";
KPT::Kernel::Version "2.4.27";