使ったことないけど、この辺り？ https://github.com/apple/swift-evolution/blob/main/proposals/0219-package-manager-dependency-mirroring.md

swift-evolution/0219-package-manager-dependency-mirroring.md at mai...

This maintains proposals for changes and user-visible enhancements to the Swift Programming Language. - swift-evolution/0219-package-manager-dependency-mirroring.md at main · apple/swift-evolution