Testing org.kde.Platform flatpak built in CI

Very technical post, feel free to ignore if you're not working on KDE stuff.

Since I'm on KDE Linux, I use flatpak apps for pretty much everything, such as Kontact suite. I wanted to test out how my Breeze changes would look like in KMail and other apps, but I didn't want to build the whole PIM stack.

Here's how I tested it by building the flatpak-kde-runtime in CI, downloading the built files and using it as a repository for testing any changes to org.kde.Platform locally.

1. First make changes to the flatpak-kde-runtime, such as this here: https://invent.kde.org/packaging/flatpak-kde-runtime/-/commits/work%2Fakselmo%2Ftest-breeze
2. Run the CI
3. Check the pipeline ID for build-runtime-amd64
   • Click the green checkmark, its something like #1210828
4. Download the artifact from here: https://storage.kde.org/ci-artifacts/packaging/flatpak-kde-runtime/p/PIPELINE_ID_HERE/repository-x86_64.tar.gz
5. Extract the tar into some folder after downloading
6. Add it as a repository: flatpak remote-add --no-gpg-verify kde-platform-testing ./repo-x86_64
7. Uninstall the current platform: flatpak uninstall org.kde.Platform --force-remove
   • The force-remove makes sure we do not install any apps, just the platform
8. Run flatpak install org.kde.Platform
9. Select the kde-platform-testing as the repo to install from
10. Done!

Now any app that uses the version of platform (6.10 in my example) will utilize your custom built one.