Automate copyright checks (9882 companion)

[tibetiroka]

Adds the copyright CI checks from ES, though they now run unconditionally since pretty much everything should be editing the copyright file.

The only issue is that now the workflow file would probably be included in the plugin, which seems unfortunate. I think it can be solved by uploading custom artifacts to future releases, but we have to make sure it doesn't break the continuous nor the release builds.

With the included CD stuff we should be able to generate the correct artifacts, but the plugin manifest in https://github.com/endless-sky/endless-sky-plugins will likely have to be updated.

[tibetiroka]

I can't get the jobs to start. Is this a permission thing?

[quyykk]

I'm not sure why it doesn't run. Maybe it's not enabled in the repo settings? @Zitchas

Or maybe it's just a security thing since these workflow files are new.

[quyykk]

Do we really need a CD workflow?

[tibetiroka]

We need the CD if we don't want to include the .github files in the release I think?

[quyykk]

Do we really need a release CD workflow?

[tibetiroka]

This could probably be folded into the standard CD workflow, I just don't have enough experience and confidence so just copied things over from ES. File names might have to be different, idk.

[warp-core]

GitHub just won't run workflows added in a PR if the file doesn't exist in the base branch.
Actually, no, it won't run them if the file doesn't exist in the repository. If, for example, your PR head was a different branch in the same repository, it would run the workflows.

[warp-core]

I think we can have GitHub not include the workflow files in the source code archive with a .gitattributes file.
endless-sky/endless-sky does this:

# Don't export certain files via `git archive` (e.g. via "Download ZIP")
.gitattributes export-ignore
.gitignore export-ignore
.gitmodules export-ignore
.github export-ignore

Which means we don't need to make a continuous release.

Actually, we don't need the CD at all if we do that. The CD would just produce an archive with the same contents, but it'd be taking up space and would expire. The source code archives don't count towards a limited storage capacity.

[tibetiroka]

If that works, that sounds like a great solution.