Adding AppData files for frameworks

[Richard Hughes]

Hi all,

I've been trying to show the frameworks in GNOME Software this
morning, so we can click on them in the updates panel to do live
updates. Two things are clear:

 * frameworks never seem to be marked as "current" (is that a bug, or
by design?)
 * there's not enough data to show anything meaningful

Would adding an AppData file for the frameworks be okay? e.g. shipping
something like this in
/files/share/appdata/org.gnome.Platform.appdata.xml:

<?xml version="1.0" encoding="UTF-8"?>
<component type="runtime"> <!-- this is new to AppStream, MatthiasK
would need to ack this, and if he's reading this, should it be a
.metainfo.xml file too? -->
  <id>org.gnome.Platform</id>
  <metadata_license>CC0-1.0</metadata_license>
  <project_license>GPL-2.0+</project_license>
  <name>GNOME 3.20</name>
  <summary>Shared runtime for GNOME applications</summary>
  <description>
    <p>This framework provides the core libraries and executables
needed by GNOME applications.</p>
  </description>
  <releases>
    <release version="3.20.0" timestamp="1446724044">
      <description>
        <p>This is the first stable release of 3.20 fixing many bugs
and adding new features.</p>
      </description>
    </release>
  </releases>
  <url type="homepage">http://www.gnome.org/</url>
  <update_contact>alexl<at>gnome<dot>org</update_contact>
  <compulsory_for_desktop>GNOME</compulsory_for_desktop>
</component>

This could be shipped by something upstream (e.g. gnome-desktop) which
makes the translations easy (which of course we *want* to have)
although it would be odd writing update descriptions in the appdata
that lives in gnome-desktop about new things included in the
framework, or bugfixes in libraries like GTK. I'm open to ideas here.

To show anything in the updates panel we need more information than
just the xdg-app name, and we really ought to support update
descriptions and translations at a bare minimum. I don't think
screenshots are required as we'd just be showing the platform in the
updates panel, not in the main search results.

Richard