Update FAQ: double expanding the property / nested property names

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@887116 13f79535-47bb-0310-9956-ffa450edef68

docs/faq.html

@@ -1237,6 +1237,17 @@ shell-prompt> m4 foo.m4 > foo
   </sequential>
 </macrodef>
 </pre>
+                        <p>With the 'props' antlib (external, but also from Ant) you could
+         do the dereferencing with <code>${${anotherprop}</code> - not just
+         in the property task - instead everywhere in your buildfile (after
+         registering the required property helper).</p>
+                        <pre class="code">
+&lt;propertyhelper&gt;
+  &lt;props:nested /&gt;
+&lt;/propertyhelper&gt;
+&lt;property name=&quot;foo&quot; value=&quot;foo.value&quot; /&gt;
+&lt;property name=&quot;var&quot; value=&quot;foo&quot; /&gt;
+&lt;echo&gt; ${${var}} = foo.value &lt;/echo&gt;</pre>
                     <p class="faq">
       <a name="delete-directory-children-only"></a>
       How can I delete everything beneath a particular directory,

xdocs/faq.xml

@@ -745,6 +745,17 @@ shell-prompt> m4 foo.m4 > foo
   </sequential>
 </macrodef>
 ]]></source>
+         <p>With the 'props' antlib (external, but also from Ant) you could
+         do the dereferencing with <code>${${anotherprop}</code> - not just
+         in the property task - instead everywhere in your buildfile (after
+         registering the required property helper).</p>
+         <source><![CDATA[
+<propertyhelper>
+  <props:nested />
+</propertyhelper>
+<property name="foo" value="foo.value" />
+<property name="var" value="foo" />
+<echo> ${${var}} = foo.value </echo>]]></source>
       </answer>
     </faq>