implement the registry/docker-credentials endpoint (#273)

registry.go

@@ -1,7 +1,9 @@
 package godo
 
 import (
+	"bytes"
 	"context"
+	"fmt"
 	"net/http"
 )
 
@@ -16,6 +18,7 @@ type RegistryService interface {
 	Create(context.Context, *RegistryCreateRequest) (*Registry, *Response, error)
 	Get(context.Context) (*Registry, *Response, error)
 	Delete(context.Context) (*Response, error)
+	DockerCredentials(context.Context) (*DockerCredentials, *Response, error)
 }
 
 var _ RegistryService = &RegistryServiceOp{}
@@ -80,3 +83,31 @@ func (svc *RegistryServiceOp) Delete(ctx context.Context) (*Response, error) {
 	}
 	return resp, nil
 }
+
+// DockerCredentials is the content of a Docker config file
+// that is used by the docker CLI
+// See: https://docs.docker.com/engine/reference/commandline/cli/#configjson-properties
+type DockerCredentials struct {
+	DockerConfigJSON []byte
+}
+
+// DockerCredentials retrieves a Docker config file with the registry's credentials.
+func (svc *RegistryServiceOp) DockerCredentials(ctx context.Context) (*DockerCredentials, *Response, error) {
+	path := fmt.Sprintf("%s/%s", registryPath, "docker-credentials")
+
+	req, err := svc.client.NewRequest(ctx, http.MethodGet, path, nil)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	var buf bytes.Buffer
+	resp, err := svc.client.Do(ctx, req, &buf)
+	if err != nil {
+		return nil, resp, err
+	}
+
+	dc := &DockerCredentials{
+		DockerConfigJSON: buf.Bytes(),
+	}
+	return dc, resp, nil
+}

registry_test.go

@@ -80,3 +80,19 @@ func TestRegistry_Delete(t *testing.T) {
 	_, err := client.Registry.Delete(ctx)
 	require.NoError(t, err)
 }
+
+func TestRegistry_DockerCredentials(t *testing.T) {
+	setup()
+	defer teardown()
+
+	want := []byte("this is a valid docker config json")
+
+	mux.HandleFunc("/v2/registry/docker-credentials", func(w http.ResponseWriter, r *http.Request) {
+		testMethod(t, r, http.MethodGet)
+		w.Write(want)
+	})
+	got, _, err := client.Registry.DockerCredentials(ctx)
+
+	require.NoError(t, err)
+	require.Equal(t, want, got.DockerConfigJSON)
+}