From 73e79a3310f3976b61a295f45e12aead9af41962 Mon Sep 17 00:00:00 2001
From: Nan Monnand Deng <monnand@gmail.com>
Date: Mon, 1 Jul 2013 17:57:56 -0400
Subject: [PATCH] reduce the number of string copy operations.

---
 registry/registry.go | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/registry/registry.go b/registry/registry.go
index 0840ffbb83..03a2890105 100644
--- a/registry/registry.go
+++ b/registry/registry.go
@@ -116,9 +116,11 @@ func (r *Registry) setUserAgent(req *http.Request, extra ...VersionChecker) {
 	if len(r.baseVersions)+len(extra) == 0 {
 		return
 	}
-
-	userAgent := appendVersions(r.baseVersionsStr, extra...)
-	req.Header.Set("User-Agent", userAgent)
+	if len(extra) == 0 {
+		req.Header.Set("User-Agent", r.baseVersionsStr)
+	} else {
+		req.Header.Set("User-Agent", appendVersions(r.baseVersionsStr, extra...))
+	}
 	return
 }