proposal: package change metadata

We're working on bodhi-scraper which is part of larger effort in rpm-ostree to optimize packing images.

We require a metadata file (frequencyUpdateInfo.json) in the repodata of every (Fedora/RHEL/SCOS/Kionite)<Release> repository. This file will contain the list of all updates to all of the packages of the specific release.

These list of updates are more comprehensive than those present in updateinfo.xml.

We then combine the frequencyUpdateInfo.json of all the current and pending releases and process it to create a file.

Since this file will be required for all rpm-ostree based Linux distributions, we wanted the architecture to integrate with createrepo_c to make the implementation more general.

Option 1: Inject this into primary.xml

Since this is a relatively small amount of additional metadata per package, we could add it to the primary package metadata. primary.xml is already enormous.

Option 2: Add a new updatemeta.json

We could introduce a new metadata file (JSON since this is 2020s) that contains this metadata instead.

Note that either option implies freezing (at least the first version of) the data shipped.