Bug#1075819: apt list --upgradable does not reflect snapshot state

[Noah Meyerhans <noahm@debian.org>]

Package: apt
Version: 2.9.5
Severity: normal
X-Debbugs-Cc: noahm@debian.org

apt does not appear to to be able to list upgradable packages when they come
from a snapshot.

root@c6220891b564:/# apt -S 2024-06-30T00:05:09Z update
Hit:1 http://10.212.0.5/snapshot/2024-06-30T00:05:09Z/debian trixie InRelease
Hit:2 http://10.212.0.5/snapshot/2024-06-30T00:05:09Z/debian trixie-updates InRelease
Hit:3 http://10.212.0.5/snapshot/2024-06-30T00:05:09Z/debian trixie-backports InRelease
Hit:4 http://10.212.0.5/debian-security/snapshot/2024-06-30T00:05:09Z/debian-security trixie-security InRelease
Hit:5 https://deb.debian.org/debian trixie InRelease
Hit:6 https://deb.debian.org/debian trixie-updates InRelease
Hit:7 https://deb.debian.org/debian trixie-backports InRelease
Hit:8 https://deb.debian.org/debian-security trixie-security InRelease
2 packages can be upgraded. Run 'apt list --upgradable' to see them.

root@c6220891b564:/# apt list --upgradable
root@c6220891b564:/# 

root@c6220891b564:/# apt -S 2024-06-30T00:05:09Z list --upgradable
Error: Command line option 'S' [from -S] is not understood in combination with the other options.

root@c6220891b564:/# apt -S 2024-06-30T00:05:09Z --assume-no dist-upgrade
Upgrading:
  libzstd1  mawk

Summary:
  Upgrading: 2, Installing: 0, Removing: 0, Not Upgrading: 0
  Download size: 391 kB
  Space needed: 1024 B / 26.8 GB available

Continue? [Y/n] N
Abort.

I would expect one of the `list` invocations to be able to show the list of
packages that would be upgraded with the `dist-upgrade` invocation.  I'm not
entirely sure which it should be, but I think for consistency it should be
the one that includes the `-S` flag.

The relevant apt configuration involved in this example is:

root@c6220891b564:/# cat /etc/apt/sources.list.d/debian.sources
Types: deb deb-src
URIs: https://deb.debian.org/debian
Suites: trixie trixie-updates trixie-backports
Components: main
Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg
Snapshot: yes

Types: deb deb-src
URIs: https://deb.debian.org/debian-security
Suites: trixie-security
Components: main
Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg
Snapshot: yes
root@c6220891b564:/# cat /etc/apt/apt.conf.d/90snapshot
APT
{
  Snapshot "2024-06-27T19:18:25Z";
};

Acquire
{
  Snapshots::URI
  {
    Label::Debian "http://10.212.0.5/snapshot/@SNAPSHOTID@/debian/";;
    Label::Debian-Security "http://10.212.0.5/debian-security/snapshot/@SNAPSHOTID@/debian-security/";;
    "Label::Debian Backports" "http://10.212.0.5/snapshot/@SNAPSHOTID@/debian/";;
    Override::Label::Debian "http://10.212.0.5/snapshot/@SNAPSHOTID@/debian/";;
    Override::Label::Debian-Security "http://10.212.0.5/debian-security/snapshot/@SNAPSHOTID@/debian-security/";;
    "Override::Label::Debian Backports" "http://10.212.0.5/snapshot/@SNAPSHOTID@/debian/";;
  };
};