Comment 2 for bug 1678670

The basic idea of AppStream language packs is that you can drop in as many as you want.

E.g. if Firefox has it's l10n data split into different packages, each one of these will get one AppStream metainfo snippet in /usr/share/metainfo describing which language the langpack supports and what software component it is for (in case of KDE, there will be multiple components).
The software center is supposed to check which software is installed and if there are language packs available for the current language, and then install them transparently.

So, what GNOME Software does now is pretty tailored to Fedora's way of doing things, and GS might need to be adjusted for this to work (otherwise the Addons->Langpacks menu will be pretty full of language packs for all kinds of stuff). One thing I could imagine is GS just grouping all language packs together by locale, and then only install the necessary bits if someone hits "Install" on one.

As for the generation of metainfo files, I wanted to add some small helper code to the cli tool, so we can quickly auto-generate them by a script at package build-time and don't need to fiddle with XML much.