Bug#337157: apt-get update package list files deleted

[Adrian Jackson <adrianjackson@tele2.fr>]

Package: apt
Version: 0.6.42.1
Severity: normal

If I run "apt-get update" when my modem is disconnected, files downloaded by ftp
are deleted. 

With older versions of apt, existing ftp files were merged with the package list
from my local archive. This was useful as it allowed me to :
	make changes to my local archive
	update the package cache just to take account of these changes.
	
I do not have a fast internet connection and it takes me 15 minutes to download
package lists.

-- Package-specific info:

-- apt-config dump --

APT "";
APT::Architecture "i386";
APT::Build-Essential "";
APT::Build-Essential:: "build-essential";
Dir "/";
Dir::State "var/lib/apt/";
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/apt/";
Dir::Cache::archives "archives/";
Dir::Cache::srcpkgcache "srcpkgcache.bin";
Dir::Cache::pkgcache "pkgcache.bin";
Dir::Etc "etc/apt/";
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";
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";

-- (no /etc/apt/preferences present) --


-- /etc/apt/sources.list --

# sources.list for apt
deb http://security.debian.org/ testing/updates main contrib 

deb file:/archive linux-packages/
deb http://ftp.fr.debian.org/debian testing main contrib

-- System Information:
Debian Release: testing/unstable
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: i386 (i686)
Shell:  /bin/sh linked to /bin/bash
Kernel: Linux 2.6.8
Locale: LANG=fr_FR, LC_CTYPE=fr_FR (charmap=ISO-8859-1)

Versions of packages apt depends on:
ii  libc6                         2.3.5-6    GNU C Library: Shared libraries an
ii  libgcc1                       1:4.0.2-2  GCC support library
ii  libstdc++6                    4.0.2-2    The GNU Standard C++ Library v3

apt recommends no packages.

-- no debconf information