diff -r 2a47b00f60b0 -r d83b10c210e3 lib/http.py
--- a/lib/http.py	Fri Feb 06 23:21:24 2009 +0200
+++ b/lib/http.py	Fri Feb 06 23:55:23 2009 +0200
@@ -41,6 +41,34 @@
 
         return os.path.dirname(self.env['SCRIPT_NAME'])
     
+    def get_page_prefix (self) :
+        """
+            Returns the URL path root for page URLs, based on REQUEST_URI with PATH_INFO removed
+
+            /                   -> 
+            /foo.cgi            -> /foo.cgi
+            /foo.cgi/index      -> /foo.cgi
+            /foo.cgi/quux/bar   -> /foo.cgi
+            /quux/foo.cgi/bar   -> /quux/foo.cgi
+            /bar                -> 
+        """
+        
+        # XXX: request uri path without the query string
+        request_path = self.env.get('REQUEST_URI', '').split('?', 1)[0].rstrip('/')
+
+        # path info
+        page_name = self.get_page_name()
+
+        # special-case for empty page_name
+        if not page_name :
+            return request_path
+        
+        # sanity-check
+        assert request_path.endswith(page_name)
+        
+        # trim
+        return request_path[:-len(page_name)].rstrip('/')
+
     def get_page_name (self) :
         """
             Returns the requested page path with no leading slash, i.e.