[repo-coord] disttags, useful?? (was Re: python 2.3 for RH7.3)

[Jeff Pitman]

(moved this out to repo-coord)

Background Info

Pondering upon the true usefulness of disttags given observations seen 
while performing apt-get dist-upgrade.

On Sunday 19 December 2004 10:28, Axel Thimm wrote:
> On Sat, Dec 18, 2004 at 10:59:28PM +0800, Jeff Pitman wrote:
> > On Saturday 18 December 2004 10:20, Axel Thimm wrote:
> > > I guess you must have had a bad repo in the set. The sets I have
> > > successfully been upgrading were
> > > vendor/atrpms/freshrpms/newrpms/dag/kde-redhat.
> >
> > So, there's a lot of resulting cruft
> > unless we could somehow detect that among all the active repos
> > whether a particular version of a package is really needed.  Pretty
> > tough hurdle to jump over.
>
> Now that you mention it I remember that freshrpms and perhaps even
> dag removed the epochs from their packages at some time
> (rh9?). Unfortunatley epochs are fatal sins, once there you may not
> remove them, otherwise you get effects like the ones you describe.

My gut feeling without any anecdotal evidence is that Epochs aren't the 
only problem.  Another issue could be package renames between distro 
versions, such as libgal2.0_6 versus libgal2 or other small tweaks like 
this.   One other, I'd like to highlight, is the existence of rhfc2 
packages in ATrpms, Dag, Freshrpms, CCRMA, etc.  Yes, since the glibc 
and base packages between fc2 && fc3 provide the same, these are good 
to go.  So, what's the usefulness?

Therefore, it is my belief that delegating this high level function to 
another mechanism rather than utilizing the existing depresolver via 
Release: would be more flexible and more useful. 

> Apart from that the concept of each repo until now is to ensure
> proper upgradablity. If that is not sustained it's a bug in the repo.

Unfortunately, we don't have enough testing in the dist-upgrade arena. 
So, I believe that dist-upgrade is the only target usefulness for 
disttags.  However, since this happens on a per machine basis maybe 
once every 1 or 2 years depending on required stability, it's real 
tough to get anything out of it.

So, cases against disttag usefulness:

1. Same repo, but later distro no longer provides package because it's 
been put into Fedora Core/Extras.
2. Package renames. (libgal2.0_6 versus libgal2)
3. Reuse of packages just used in another distro (fc2 versus fc3)
4. epoch'd disttag vs. "rhfc2"; migration to rhfc2 format requires an up 
on the Release for all packages.

Anyway, there might be other issues, but I feel these provide a 
compelling look at a possible rethink on disttags.  Let me know where 
I've gone absolute mad.

take care,
-- 
-jeff