Re: Transitional (dummy) packages considered silly

[Goswin von Brederlow <goswin-v-b@web.de>]

Guillem Jover <guillem@debian.org> writes:

> On Wed, 2009-09-23 at 10:51:50 +0200, Goswin von Brederlow wrote:
>> Magnus Holmgren <holmgren@debian.org> writes:
>> > When a binary package is renamed or split, as well as if several packages are 
>> > merged under a new name, transitional packages are normally created, which 
>> > depend on the new packages, which in turn Replaces and Conflicts with, and 
>> > possibly Provides, the old packages. I find those dummy packages as silly to 
>> > create as to uninstall after upgrading.
>> 
>> Dpkg has the ability to vanish empty packages. A dummy package should
>> be completly empty and not even contain a /usr/share/doc/. That way on
>> installation the package pulls in its depends and then vanishes. So no
>> more need to uninstall after upgrading. This only works if the
>> superseeding packages Provide the old one though. Otherwise depends on
>> the old package would become unsatisfied.
>
> That's not correct. dpkg only disappears packages that have been
> completely replaced while installing other packages. There's two cases
> for this:
>
>  1. The package to disappear has files that get completely replaced by
>     the new one. Needs the Replaces field.
>  2. The disappearing package contains empty directories, and all of
>     them are shipped as well by the new package. Does not need
>     Replaces field, because directory takeover is an implicit
>     Replaces, so this is actually a subcase of 1.
>
> dpkg will never disappear a packages just because it's empty w/o the
> previous conditions. And just to clarify, in no case the Provides field
> plays any role in the disappearing process.
>
> regards,
> guillem

Ok, so one would need to have at least an empty directory (say /usr)
in the package for it to disapear? Why the distinction?

MfG
        Goswin