http.c: Avoid username prompt for certifcate credentials

If sslCertPasswordProtected is set to true do not ask for username to decrypt rsa key. This question is pointless, the key is only protected by a password. Internaly the username is simply set to "".

Signed-off-by: Rene Bredlau <git@unrelated.de>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

http.c

@@ -236,6 +236,7 @@ static int has_cert_password(void)
 		return 0;
 	if (!cert_auth.password) {
 		cert_auth.protocol = xstrdup("cert");
+		cert_auth.username = xstrdup("");
 		cert_auth.path = xstrdup(ssl_cert);
 		credential_fill(&cert_auth);
 	}