add better generate

Signed-off-by: Jess Frazelle <acidburn@microsoft.com>

vendor/github.com/genuinetools/reg/registry/ping.go

@@ -0,0 +1,12 @@
+package registry
+
+// Ping tries to contact a registry URL to make sure it is up and accessible.
+func (r *Registry) Ping() error {
+	url := r.url("/v2/")
+	r.Logf("registry.ping url=%s", url)
+	resp, err := r.Client.Get(url)
+	if resp != nil {
+		defer resp.Body.Close()
+	}
+	return err
+}