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Re: postrm::downgrade?



On Mon, Jul 07, 2003 at 02:07:34PM +0800, Niall Young wrote:

> > > How about a postrm::downgrade hook to reverse any changes made in the
> > > new version's preinst::upgrade so that when the old version's
> > > preinst::upgrade
> > > is applied you're not left with a potential mix of configuration?
> > > seamlessly - i.e. reverse all changes made in the upgrade.  Is there
> > > another way?

> > You'd need more than that. Apt would need to be changed to handle
> > undoing of package splitting (Conflicts/Replaces), and is not always
> > possible anyway, new packages, might use new file-formats which can be
> > converted from the old-version but not back again.

> Yeah - it's a minefield of nightmares I know.  Debian handles upgrades
> really well, but downgrades aren't as seamless.  A postrm::downgrade
> hook is a pretty major change, it would take years to roll out - just
> wondering if anyone has thought about the problem before and if/when
> Debian could address this?

Never.  This is not an effective use of developer time -- there are
enough bugs with *upgrading* packages yet that we don't need to be
worried about supporting downgrades.

If you want individual maintainer scripts to support downgrading, dpkg
already gives you everything you need:  just compare the value of $2
with the current version to detect whether it's an upgrade or downgrade,
and handle appropriately.  But I'm not likely to accept patches for this
on any of my packages, as I don't believe this is useful enough to
justify the added complexity.

-- 
Steve Langasek
postmodern programmer

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