Check for updates to shared-modules submodule

[nanonyme]

This is only loosely part of manifest IOW it's tracked externally, then included into manfiest. It would be great to have it automatically updated as well though to make sure everyone gets to benefit of improvements done to shared-modules.

[gasinvein]

This is to some extent similar to #161

[wjt]

I can't find where this was discussed before. IMO it is fine to just chase the tip of shared-modules and other submodules, but I think the change should only be proposed if it updates a file in the submodule which the manifest actually uses. Otherwise every commit to shared-modules will trigger hundreds of useless PRs

[wjt]

Found it! https://github.com/flathub/flathub/pull/1372

[gasinvein]

the change should only be proposed if it updates a file in the submodule which the manifest actually uses

That's good idea. But it would require noticeably more complex logic. Moreover, not all git submodules contain flatpak-builder modules, e.g. in the Telegram flatpak we have a git submodule with a set of patches.

[dreua]

In the meantime everyone who wants can use dependabot to check for submodule updates.