Modify an existing reference by adding nested elements or (re-)assigning properties
mapped as XML attributes. This is an unusual task that makes use of Ant's internal
processing mechanisms to reload a previously declared reference by means of the 'id'
attribute, then treats the declared augment element as though it were the
original element.
Since Apache Ant 1.8.1
| Attribute | Description | Required | 
| id | The id of the reference to augment. If no such reference has
      been declared a BuildExceptionis generated. | Yes | 
Additional permissible attributes are dependent on the reference to be modified.
Permissible nested elements are dependent on the reference to be modified.
  <fileset id="input-fs" dir="${basedir}" />
<augment id="input-fs" excludes="foo" />
Modifies the excludes attribute of input-fs.
  <augment id="input-fs">
    <filename name="bar" />
  </augment>
Adds a filename selector to input-fs.