Description

As Docker supports more and more platforms, but also cross-platforms use cases (e.g., Windows client interacting with a Linux daemon, OSX client interacting with a Windows daemon, ...), the user-agent string when interacting with Registry should reflect that.

How to

Have the docker client pass down its own portion of the user-agent string, that the daemon will complete.

Ping @rogaha @thaJeztah @docker/distribution-maintainers @friism