flatpak should have a way to list available extensions

[matthiasclasen]

it would be nice if I could answer a question like "what icon themes are available for flatpak" by running something like

flatpak remote-ls --extension org.freedesktop.Platform.Icontheme flathub

flatpak remote-ls --runtime flathub | grep ^org.freedesktop.Platform.Icontheme

comes close. Maybe this is good enough...

[alexlarsson]

Right now we just have to types "apps" and "non-apps" (the latest being runtime/... refs). This is a bit unfortunate, as it makes it hard to list "all extensions" without parsing all metadata files to see what possible extension point names there are...
I wonder if we could do some magic on the repo side and put this in the summary file. On the other hand, those are already pretty large...

[alexlarsson]

I guess the summary file has all the metadata files already, so we could figure it out locally.