Index: trac/ticket/templates/ticket.html
===================================================================
--- trac/ticket/templates/ticket.html	(revision 5220)
+++ trac/ticket/templates/ticket.html	(working copy)
@@ -195,6 +195,15 @@
                       <py:when test="field_name == 'attachment'">
                         <a href="${href.attachment('ticket', ticket.id, field.new)}"><em>${field.new}</em></a> added
                       </py:when>
+                      <py:when test="field_name == 'cc'">
+                        <py:with vars='newcc=map(lambda s: s.strip(), field.new.split(",")); 
+                                       oldcc=map(lambda s: s.strip(), field.old.split(","));
+                                       added=", ".join([x for x in newcc if x and x not in oldcc]);
+                                       removed=", ".join([x for x in oldcc if x and x not in newcc])'>
+                          <py:if test='added'>added: <em>${added}</em></py:if><py:if test='added and removed'>;</py:if>
+                          <py:if test='removed'>removed: <em>${removed}</em></py:if>
+                        </py:with>
+                      </py:when>
                       <py:when test="field.old and field.new">
                         changed
                         <py:choose>