Install appdata files to /usr/share/metainfo/

[sidt4]

$ apt-file search /usr/share/appdata/
warzone2100: /usr/share/appdata/net.wz2100.warzone2100.appdata.xml

...

• Refer: https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html#spec-component-location
• Refer: https://appstream.debian.org/sid/main/issues/warzone2100.html
• Refer: https://appstream.debian.org/sid/main/metainfo/warzone2100.html

[sidt4]

Notes:

• Use appstreamcli validate ( and not the deprecated appstream-util validate ) command to validate appstream metainfo files.
• The metainfo link above contains fallback appdata generated from .desktop file ( if the appdata in not installed in /usr/share/metainfo/ )

[past-due]

There were some historical reasons to use the original /usr/share/appdata/ path, but it's probably about time we can update this to /usr/share/metainfo/

(For building the Flatpak, we do already use appstreamcli validate: https://github.com/Warzone2100/warzone2100/blob/d92ee42e7b5a14357f287c30490c56cd7dc08d71/.ci/flatpak/build.sh#L42C3-L42C24)

[past-due]

PR #3423 makes some improvements to the appstream file info.

Of note: we were actually already installing it to /usr/share/metainfo/

The report you referenced seems to be in regards to the debian repo's package - you would probably want to contact the debian maintainers to get that fixed.