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Re: Planning for libidn shared library version transition

On Wed, 26 May 2021 at 19:18:24 +0200, Simon Josefsson wrote:
> Andreas Metzler <ametzler@bebt.de> writes:
> > Why not use a versioned Provides *instead* of the dummy package?
> Yeah, I never understand exactly when these dummy packages are needed.

My understanding is that they are usually still necessary for smooth
upgrades from one stable release to the next, because apt's dependency
resolver tries not to remove packages (to minimize risk of removing
something you were relying on), and removing a "real" libidn11-dev
package because its lockstep version dependency is no longer satisfiable
will still count as removing a package, even if a new libidn-dev now
Provides it.

It's a probabilistic thing, because apt calculates a "score" for various
options for the whole upgrade transaction and chooses the one with the
highest score - on some systems it will be able to figure out the right
upgrade transaction even without a transitional package, but on others it
will not. Having a transitional package makes it more likely that the
intended upgrade happens, because apt gives a high "score" to upgrading a
package that was already installed.

piuparts only routinely tests relatively small installations - there are
periodic QA tests done on larger systems like the union of all desktop
tasks, but those are more expensive to run.


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