Replaces, Conflicts and Provides (was Re: Upgrade procedure for tetex)

[Chow Chi-Ming <cmchow@se.cuhk.edu.hk>]

>>>>> "Chris" == Chris Fearnley <cjf@netaxs.com> writes:

Chris> 'Chow Chi-Ming wrote:'
>>
>>>>>>> "Chris" == Chris Fearnley <cjf@netaxs.com> writes:
>>
Chris> I think most of the old tex packages can be automatically
Chris> uninstalled with a variation on this.  But the tetex-base
Chris> and/or -bin need to Provides the old packages so things don't
Chris> blow up in process.
>>  I am confused.  What are these ``things'' and how will they ``blow
>> up''?  The package mentioned in the Provides field are virtual
>> package names.  Do we have an alternative (La)TeX system in Debian
>> so that we need virtual packages?

Chris> "Blow up" is my way of saying dselect will complain loudly.
Chris> One can use Provides to give dpkg assurances that the upgrade
Chris> will work.  Conceptually this use of Provides differs from
Chris> virtual packages.  The idea is that the new tetex packages
Chris> should provide the old TeX packages so dpkg will allow the old
Chris> tex packages to be replaced.

We really need some help from dpkg/dselect experts here.  From my
programmer's manual (2.1.1.0) the purpose of Provides: is to give
virtual package names.  And I am under the impression that a package
will be replace/removed _without_ it being provided by some other
packages.  

For example, the package fileutils Replaces and Conflicts color-ls but
there is no color-ls package anymore and no other package Provides
color-ls.  This doesn't stop the old color-ls package being replaced
_completely_ by fileutils.  I tought this is the way to obsolete a
package, right?

tetex packages are using exactly the same mechanism but dpkg doesn't
seem to be able to remove multiple old packages.

--
Billy C.-M. Chow <cmchow@se.cuhk.edu.hk>
Department of Systems Engineering       
The Chinese University of Hong Kong