From b49074eb6b19d8f5fdb3301a6e50f11845dd530d Mon Sep 17 00:00:00 2001
From: Markus Unterwaditzer <markus@unterwaditzer.net>
Date: Mon, 11 Aug 2014 11:56:25 +0200
Subject: [PATCH] Add documentation about url_for's default scheme

Fix #1129
---
 flask/helpers.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/flask/helpers.py b/flask/helpers.py
index 77148708..37843a4c 100644
--- a/flask/helpers.py
+++ b/flask/helpers.py
@@ -248,7 +248,10 @@ def url_for(endpoint, **values):
       address can be changed via `SERVER_NAME` configuration variable which
       defaults to `localhost`.
     :param _scheme: a string specifying the desired URL scheme. The `_external`
-      parameter must be set to `True` or a `ValueError` is raised.
+      parameter must be set to `True` or a `ValueError` is raised. The default
+      behavior uses the same scheme as the current request, or
+      ``PREFERRED_URL_SCHEME`` from the :ref:`app configuration <config>` if no
+      request context is available.
     :param _anchor: if provided this is added as anchor to the URL.
     :param _method: if provided this explicitly specifies an HTTP method.
     """