@@ -18,11 +18,11 @@ type UAStringKey struct{}

 //

 //	[docker client's UA] UpstreamClient([upstream client's UA])

 func DockerUserAgent(ctx context.Context) string {

-	daemonUA := getDaemonUserAgent()

-	if upstreamUA := getUserAgentFromContext(ctx); len(upstreamUA) > 0 {

-		return insertUpstreamUserAgent(upstreamUA, daemonUA)

+	ua := getDaemonUserAgent()

+	if upstreamUA := getUpstreamUserAgent(ctx); upstreamUA != "" {

+		ua += " " + upstreamUA

 	}

-	return daemonUA

+	return ua

 }

 var (

@@ -57,16 +57,23 @@ func getDaemonUserAgent() string {

 	return daemonUA

 }

-// getUserAgentFromContext returns the previously saved user-agent context stored in ctx, if one exists

-func getUserAgentFromContext(ctx context.Context) string {

+// getUpstreamUserAgent returns the previously saved user-agent context stored

+// in ctx, if one exists, and formats it as:

+//

+//	UpstreamClient(<upstream user agent string>)

+//

+// It returns an empty string if no user-agent is present in the context.

+func getUpstreamUserAgent(ctx context.Context) string {

 	var upstreamUA string

 	if ctx != nil {

-		var ki interface{} = ctx.Value(UAStringKey{})

-		if ki != nil {

+		if ki := ctx.Value(UAStringKey{}); ki != nil {

 			upstreamUA = ctx.Value(UAStringKey{}).(string)

 		}

 	}

-	return upstreamUA

+	if upstreamUA == "" {

+		return ""

+	}

+	return fmt.Sprintf("UpstreamClient(%s)", escapeStr(upstreamUA))

 }

 const charsToEscape = `();\`

@@ -89,11 +96,3 @@ func escapeStr(s string) string {

 	}

 	return ret

 }

-

-// insertUpstreamUserAgent adds the upstream client useragent to create a user-agent

-// string of the form:

-//

-//	$dockerUA UpstreamClient($upstreamUA)

-func insertUpstreamUserAgent(upstreamUA string, dockerUA string) string {

-	return fmt.Sprintf("%s UpstreamClient(%s)", dockerUA, escapeStr(upstreamUA))

-}