Bug#954807: apt upgrade sometimes marks packages as manually installed

[Piotr Engelking <inkerman42@gmail.com>]

Julian Andres Klode <jak@debian.org>:

> This is not a bug, but a feature. You ran the equivalent of
> apt install libc6 && apt upgrade, and that causes libc6 to be
> manually installed, because you manually requested it to be
> installed.

Hmm... What is the difference between apt install <pkg> and apt upgrade
<pkg>, then? I would naively expect the first to mark the package as
manually installed, and the second not to. Is there a way to to upgrade
a package to a particular release without marking it as manually
installed?

Also, when the package listed as argument to apt upgrade is not at the
requested version, it is not marked as manually installed, exactly as I
would expect.