Bug#1102604: rescue-mode: Provide rootfs subvolume selection menu

[Pascal Hambourg <pascal@plouf.fr.eu.org>]

On 27/12/2025 at 12:53, Martin-Éric Racine wrote:
> la 27.12.2025 klo 13.44 Cyril Brulebois (kibi@debian.org) kirjoitti:
> > Just out of curiosity, since we support a number of scenarios, which
> > one was that? In case someone else wants to chime in and test another
> > one…
> >
> > Condensing the changelog:
> >
> >      1. The default installation to @rootfs (bullseye and later)
> >      2. The default installation to subvolid=5 (buster or earlier).
> >         "subvolid=5" was chosen over "subvol=/" for maximum disambiguation.
> >      3. Add support for rescuing btrfs systems installed via the Calamares
> >         installer found on Debian Live images: it uses subvol=@ (instead of
> >         subvol=@rootfs as seen with debian-installer).
>
> This /etc/fstab says 'defaults,subvol=/@rootfs' which IIRC was setup
> using a Bookworm installer.

I quickly tested in a VM that it works as expected in the 3 scenarios.