support cross-repository screenshot mask

[cfm]

Describe the problem

freedomofpress/securedrop stores its screenshots in freedomofpress/securedrop-docs. We don't want to store them directly in the securedrop repository. Instead, we'd like to be able to set the screenshot mask of securedrop's Weblate component to the corresponding mask within the securedrop-docs repository.

Describe the solution you'd like

We've thought of three options:

1. Support internal (weblate://) urls in the Component.screenshot_filemask field, so that we can add securedrop-docs as a component (whether or not actually translated) and refer to it that way from the securedrop component.
2. Support submodules, so that securedrop can pull in securedrop-docs without containing its Git objects directly.
3. Support Git LFS, so that securedrop can pull in securedrop-docs without containing its file content directly.

Describe alternatives you've considered

No response

Screenshots

No response

Additional context

Our use-case is described in freedomofpress/securedrop#6968.

[nijel]

AFAIK git-lfs should be supported, at least I saw some reports about that. Not sure if that is the best approach for this.

[nijel]

I don't think 1 is a viable approach. Introducing fake components just to mirror another repository is not something we want to encourage. So that really leaves 2 and 3. I know some projects on Hosted Weblate are using Git LFS, but probably not for content used by Weblate, so there might be some bits of the support missing.

[github-actions]

This issue has been put aside. It is currently unclear if it will ever be implemented as it seems to cover too narrow of a use case or doesn't seem to fit into Weblate.

Please try to clarify the use case or consider proposing something more generic to make it useful to more users.