Jakub Bielecki

Change Registry.Ping() to: - respect http 401 response code as valid - conform to the Specs by requiring header Docker-Distribution-API-Version Change the TokenTransport unit tests to emit that header. Remove...

behavior of ping is against Docker v2 API Spec

2

Per [Docker v2 API Specification](https://docs.docker.com/registry/spec/api/): > When a `200 OK` or `401 Unauthorized` response is returned, the “Docker-Distribution-API-Version” header should be set to “registry/2.0”. Clients may require this header value...

add WithHeader and convert NewClient to use options

2

### Primary Motivation Described in internal ticket ENG-20050. This change is related to one of EM projects. ### Description ~Add yet another constructor in order to provide means for callers...

This fixes a race happening in the mock of `4-graceful-sigint`: ``` $ cd 4-graceful-sigint $ go run -race . Process running...^C================== WARNING: DATA RACE Read at 0x00c00001415f by goroutine 10:...