document extending config

Author: Richard Jones

doc/customizing.txt

@@ -2,7 +2,7 @@
 Customising Roundup
 ===================
 
-:Version: $Revision: 1.212 $
+:Version: $Revision: 1.213 $
 
 .. This document borrows from the ZopeBook section on ZPT. The original is at:
    http://www.zope.org/Documentation/Books/ZopeBook/current/ZPT.stx
@@ -347,6 +347,26 @@ variables not in the "main" section are referred to using their section and
 name, so "domain" in the section "mail" becomes MAIL_DOMAIN. The
 configuration variables available are:
 
+Extending the configuration file
+--------------------------------
+
+You can't add new variables to the config.ini file in the tracker home but
+you can add two new config.ini files:
+
+- a config.ini in the ``extensions`` directory will be loaded and attached
+  to the config variable as "ext".
+- a config.ini in the ``detectors`` directory will be loaded and attached
+  to the config variable as "detectors".
+
+For example, the following in ``detectors/config.ini``::
+
+    [main]
+    qa_recipients = [email protected]
+
+is accessible as::
+
+    db.config.detectors['QA_RECIPIENTS']
+
 
 Tracker Schema
 ==============