Gitweb linking to bug-tracking system

HEllo,
I have installed gitweb using git version 1.6.3.3 on ubuntu, and
everything is working perfectly. 
However, when a commit have a comment containing a string matching
"DEF[0-9]+", an hyperlink is generated on the web interface which makes
me think it is possible to link to some DTS. Yet I cannot find how to
configure this ? 

Am I missing something ? Is this totally unrelated to DTS ?

Regards,

-- 
Arnaud Bailly -- OQube
<software engineering>
http://www.oqube.com/