Deployments should be able to customize exports

[cosimoc]

In Endless we have some Flatpak applications that export additional files to the operating system -- see e.g. this patch: endlessm/flatpak@c18bf31

That is of course less than ideal, because it requires the build system to ship a forked flatpak to support this.
This sounds like something that would be useful in general, and I'd like to propose two changes:

• move the export list from build to deploy; at least this would allow not to require a custom flatpak to build those applications that want to export additional files
• move the export list not to be hardcoded, so that different deployments can customize it without requiring a patch to flatpak

CC @ramcq @erikos

[matthiasclasen]

The docs for flatpak build-finish say:

   You should review the exported files and the application metadata before creating and
   distributing an application bundle.

Doesn't that hint at the fact that you are expected to not treat the builtin list as gospel, but tweak exports according to your needs ?

I guess there is still an argument to be made that flatpak builder could support this in the manifest in some convenient way.

[cosimoc]

@matthiasclasen I am a bit confused; how is one supposed to add to that export list? flatpak-builder will call flatpak build-finish and I don't see how one would be able to change what gets exported.

[alexlarsson]

I'm currently working on adding a whitelist that is used when deploying. I would love a patch to that to make the set of allowed exports be configured at the site.

However, we can't drop the exports list during build, because we don't want to export all of share/*. I think we need an argument to build-finish for extra directories to export. Would love a patch for that too.

[alexlarsson]

Here is the whitelist: e8369a6