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Re: Bug#709758: Replacing a binary package by another one(was: Communication issue?)

On Wed, Sep 4, 2013 at 8:59 PM, Sune Vuorela <nospam@vuorela.dk> wrote:
> On 2013-09-04, Steve Langasek <vorlon@debian.org> wrote:
>> Unless apt has gotten smarter recently (which is not out of the question),
>> no.  It's a common misconception that apt will care about Provides/Replaces
>> for selecting new packages on dist-upgrade, but while it seems like a nice
>> idea, TTBOMK it's never been implemented.

The policy defines two uses of Replaces:
7.6.1 Overwriting files in other packages – this is completely ignored by APT
as that could be anything from "replacing a single file" over "fighting with
this package over a few filenames" to "replacing all files".
7.6.2 Replacing whole packages, forcing their removal – there is the common
believe that this allows all kinds of magic to happen, but no, it doesn't:
The hole paragraph doesn't mention upgrades once, because there is no
upgrade path. Not between mail-transport-agents, httpds, editors, "node",
"git" or "mplayer" packages (random examples, no critic).

So my simple question is, which combination of relations should that
be that tells a smart package manager to upgrade pkgA to pkgB ?

And does this combination also survives in the real world in which many
maintainers e.g. still haven't got the difference between breaks and
conflicts or depends, recommends and suggests?

> Over in RPM land, I think they have a Obsoletes relation for a 'you
> should consider this package a successor to <other> package'

APT has support for it since 2001. No idea how functional it is nowadays
though as the apt-rpm fork from there this probably came is just as frozen.
There should be a discussion about it in that timeframe, too. I remember
seeing one at some point in my history-digging, can't find it now though.

I think the most interesting point against such a relation might be:
Package: aptitude
Obsoletes: apt

(Not that we would be in a fight, but many people think we are, so lets
 just add some fuel for them. KDE & Gnome works just as well)

Best regards

David Kalnischkies

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