Sid installer broken - wrong branch in apt sources.list

[jnqnfe <jnqnfe@gmail.com>]

Package: debian-installer

I have a Debian live image based on Sid that I built a couple of weeks
ago. I opted to build a proper copy of the Debian installer into this
(not the default "live" installer). This installer is unmodified, just
copied from
<mirror>/dists/sid/main/installer-amd64/current/images/cdrom.

The problem I am now finding is that although initially this installer
worked fine, now it doesn't. It fails at installing the gnome desktop
and it fails at installing grub (EFI at least).

I have figured out the cause - the installer is generating an apt
sources.list file that specifies Jessie instead of Sid.

The disk image does not include all of the necessary packages for the
installation, e.g. it does not include gnome.

So, the installer seems to install a bunch of Sid packages when
performing the base install, but then points apt to Jessie. So then when
trying to install gnome it fails due to dependency issues - some of the
installed packages (systemd and glibc I think it was) are newer than
versions explicitly required by packages to be installed from Jessie.
Similarly this causes grub installation to fail.

If I switch into a console after the base install, modify the apt
sources.list file to specify Sid instead of Jessie, and run an update &
upgrade, then going back I can then successfully install gnome and grub.

The installer current files on the mirror for Sid seem (according to
matching hashes) to be identical copies of those available for Jessie.
Surely the Sid ones should be created to write Sid to the apt
sources.list file to support pure Sid installs like this one.