git-ls-remote: send no-cache header when fetching info/refs

Proxies should not cache this file as it can cause a client to end up with
a stale version, as reported here:

http://marc.theaimsgroup.com/?l=git&m=114407944125389

Signed-off-by: Nick Hengeveld <nickh@reactrix.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-ls-remote.sh

@@ -53,7 +53,7 @@ http://* | https://* )
         if [ -n "$GIT_SSL_NO_VERIFY" ]; then
             curl_extra_args="-k"
         fi
-	curl -nsf $curl_extra_args "$peek_repo/info/refs" ||
+	curl -nsf $curl_extra_args --header "Pragma: no-cache" "$peek_repo/info/refs" ||
 		echo "failed	slurping"
 	;;