duplicated url_prefix in Flask using blueprint
===

Sorry I've searched inside the stackoverflow and googled, but no useful information found.
I have an flask application,
python version 2.6
flask version 0.9

its application hierarchy is like

      applicatoin/
         __init__.py
         app.py
         hello/
           __init__.py
           view.py
           templates/
             hello.html

both files __init__.py are empty

    app.py
    -----------------------
    from flask import Flask
    from flup.server.fcgi import WSGIServer
    from hello.view import hello
    
    app = Flask(__name__)
    app.debug = True 
    
    app.register_blueprint(hello, url_prefix='/hello')
    
    if __name__ == '__main__':
    	WSGIServer(app, bindAddress='/tmp/app.sock').run()


------

    view.py
    -----------------------
    import os
    from flask import Blueprint, render_template, abort
    from jinja2 import TemplateNotFound
    
    hello = Blueprint('hello', __name__, template_folder='templates')
        
    @hello.route('/')
    def get_index():
    	try:
    		return render_template('hello.html')
    	except TemplateNotFound:
    		abort(404)

-----

    hello.html
    -----------------------
    <!DOCTYPE html>
    <html>
        <head>
            {% block head %}
            <meta charset="utf-8">
            {% endblock %}
        </head>
        <body>
            <div>
                {% block body %}
    			<h1><a href="{{ url_for('hello.get_index') }}">Click Me</a></h1>
    	    {% endblock %}
            </div>
        </body>
    </html>

It works fine when I enter localhost:8080/hello, but turns out error if I click the link in html. I found its url value is href="/hello/hello/" (Should it be "/hello/" right?).
I know hello.get_index is mapped to "/hello/", but have no idea that the first one "hello/" comes from. Any hint is appreciated.

