document erroronmissingdir attribute for dirset. PR 50365

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@1040142 13f79535-47bb-0310-9956-ffa450edef68

docs/manual/Types/dirset.html

@@ -89,6 +89,18 @@ equivalent to an <code>&lt;and&gt;</code> selector container.</p>
       true. See <a href="fileset.html#symlink">fileset's documentation</a>.</td>
     <td valign="top" align="center">No</td>
   </tr>
+  <tr>
+    <td valign="top">erroronmissingdir</td>
+    <td valign="top">
+      Specify what happens if the base directory does not exist.
+      If true a build error will happen, if false, the dirset
+      will be ignored/empty.
+      Defaults to true.
+      <em>Since Apache Ant 1.7.1 (default is true for backward compatibility
+        reasons.)</em>
+    </td>
+    <td valign="top" align="center">No</td>
+  </tr>
 </table>
 
 <h4>Examples</h4>