Le 14/02/2018 à 18:52, Vincent Bernat a écrit :
More concrete example (now a bit in the past). On Wheezy, you want to depend on a 1.8 JRE (you package independently). You put default-jre-headless (>= 1.8). Since you have forgotten about the epoch, this pulls Wheezy default-jre-headless (1:1.7-47+deb7u2). So you add the epoch to both your own package version default-jre-headless (1:1.8-1) and to the dependency. All good. You upgrade to Jessie and rebuild everything. Jessie comes with default-jre-headless (2:1.7-52) which shadows your default-jre-headless (1:1.8-1) package.
Dear Vincent, Well, in retrospect it would have been good to declare: Depends: default-jre-headless (>= 1:1.8), default-jre-headless (<< 2:)when you first added the epoch to the Depends line. In general it's not easy to predict which future version of a package will actually break you package.
The "Provides: foo-api (>= 1.8)" mentioned elsewhere in the thread sounds also neat for java packages, but it does not seem to be implemented.
What I don't quite understand: are you distributing your own default-jre-headless package, with a version later than the one in Debian? I'm not sure overriding a "default" package with a custom one is a good idea. That depends on the context of course.
In fact, one could argue that you should perhaps Depend on a specific JRE instead (or an bunch of JREs with | in between). But I understand you are just showing a real-life example where bumping the epoch caused headaches to "someone else".
Kind regards, Thibaut.