Can't provide updates to frozen suites

[iainlane]

For Ubuntu we would like to update from the old appstream-dep11 to asgen in Xenial and Yakkety, which released with data from -dep11.

I thought we could deliver the updates via the -updates suite, as another Components and icons file: Components-fixup or so. The component would have a dataPriority higher than the release but lower than proposed and `updates.

Then the config would have something like

"Suites":
  {
    "yakkety":
      {
        "redirect-to": "yakkety-updates",
        "useIconTheme": "Humanity",
        "sections": ["main"],
        "architectures": ["amd64"]
      }
  }

redirect-to means that the output is placed in yakkety-updates/Component-fixup.tar.xz.

Questions

• How does this interact with immutable? I think redirect-to probably sort of implies immutable. But what if it is added later on after the suite has already been immutable (and the data has been dropped)?
• What about dropping data - how and when? We need to keep the data for the release so that people who don't have updates aren't broken.

[ximion]

I think we will need an Override: <origin_name> field in the YAML data for sure, so a new metadata file can override an existing one entirely.
If redirect-to is added later after the data has been dropped, the logical choice would be to regenerate the data - we would just need to ensure statistics data is kept forever.
An Override property would ideally to go together with an OriginType property, that I wanted for a while to help libappstream deduplicate data.

In any case, we will need changes on the APT hook, libappstream/AppStream and appstream-generator.
As discussed last year in person, I want this to be resolved somehow, and I ideally want this to be resolved for the next Ubuntu LTS and Debian Stable. It's just a tricky thing ;-)