support conditional ManagementLink objects

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@9964 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/model/ManagementLink.java

@@ -28,6 +28,11 @@ public abstract class ManagementLink implements ExtensionPoint, Action {
      * Mostly works like {@link Action#getIconFileName()}, except that
      * the expected icon size is 48x48, not 24x24. So if you give
      * just a file name, "/images/48x48" will be assumed.
+     *
+     * @return
+     *      As a special case, return null to exclude this object from the management link.
+     *      This is useful for defining {@link ManagementLink} that only shows up under
+     *      certain circumstances.
      */
     public abstract String getIconFileName();
 

core/src/main/resources/hudson/model/Hudson/manage.jelly

@@ -52,9 +52,11 @@
       </j:if>
       <!-- TODO: replace all the hard-coded ones with the standard extension point -->
       <j:forEach var="m" items="${it.managementLinks}">
+        <j:if test="${m.iconFileName!=null}">
           <local:feature icon="${m.iconFileName}"      href="${m.urlName}"   title="${m.displayName}">
             ${m.description}
           </local:feature>
+        </j:if>
       </j:forEach>
 
       <j:choose>