unstable + no downgrades = instability
A month ago, I could with a straight face recommend that someone wipe
Redhat off their new Alpha and install Debian, as I did. Even though
it's rough around the edges, so is Redhat - and Debian on the Alpha
was more stable and had more available packages.
Today I cannot make that recommendation - not for any good reason, but
simply because a working X for the Alpha is just not available on the
Debian web sites today, so a useful install is impossible without
herioc measures. (Today! - in a few days it'll doubtless be fixed.)
Now I'm not blaming the X maintainers or the valiant Alpha porters or
anything like that. Unstable is unstable, and Debian for the Alpha is
not yet released, period.
But there *is* something that could rather painlessly keep us out of a
situation like this, which is a little history in the archives. dpkg
can easily downgrade a package, but old packages are not available.
Not anywhere! We are thereby wasting a great deal of dpkg's power.
If it were arranged to keep N old versions of packages online, or if
some human (eg the package maintainer) were in the "delete old
version" loop and could override the default behavior and keep some
chosen old versions around, this would solve the problem in a general
fashion. For example, it would have quickly solved the big i386 perl
gripe a few weeks ago.
I'm not sure exactly how difficult this would be technically, given
the automatic update software on the archives, but it would be of
particular benefit to the non-i386 ports, and even a rube-goldberg
system to keep old versions around would be a valuable safety net for
ports in which there is no "stable" dist to fall back upon.
At first I was worried that the storage costs might be prohibitive,
but we have things like xdelta which could be used (cleverly - the
.deb innards should be exposed so xdelta can see they're gzipped) on
the .deb files to decrease the space requirements considerably.