A commonly used CI workflow [1] is to chain the following steps:
> flatpak-builder --stop-at=<module>
> flatpak build <commands to build module from local checkout>
> flatpak-builder --finish-only
Unfortunately, the last step always purge all the compilation cache
created by the first one. All build steps are marked unused by default
and since they are skipped due to the option --finish-only, all of them
are always pruned by the gc function.
As a result, flatpak-builder cache becomes useless, a full compilation
is always performed.
Improve this by not cleaning unused stages when no compilation is done
by flatpak-builder (i.e: when flatpak-builder is used with --export-only
or --finish-only option).
[1]: https://gitlab.gnome.org/GNOME/Initiatives/wikis/DevOps-with-Flatpak
Denis Ollier