Cilium: CI: Add automated check for copyright headers

[twpayne]

Proposal

I occasionally forget to add copyright headers to new files in PRs, and reviewers have had to manually comment on this. Such a check can be automated, saving reviewer time.

golangci-lint includes support for the go-header linter which can probably leveraged to implement this, at least for Go source files.

Comments? Happy to implement this if folk think it would be useful.

[aditighag]

I've added a copyright profile in Goland that automatically adds the header in new files, but your proposal is useful in general.

[sayboras]

Voted for golangci-lint with go-header, one good thing is that we don't need to introduce more tools required as part of development.

PS: I might be biased here.

[twpayne]

Quick update on this: adding the check is fairly straightforward, but it turns out that there are a lot of files that either don't have a copyright header, or have a slightly weird one. I have a WIP PR but there are still a lot of files to update. As there are other higher-priority tasks this is only getting idle cycles from me.