Ant: the subant tag

In SVN I have this hierarchy:

trunk/ --+
             |
             |
             |
             + subProjectA/ -+
             |               |
             |               +- build.xml
             |
             |
             + subProjectB/ -+
                             |
                             +- build.xml

under trunk I've added a build.xml file and using the Ant 1.6 tutorial I've added this build.xml file:

<?xml version="1.0" encoding="UTF-8"?>
<project default="dist" name="My Project">
            <macrodef name="iterate">
                <attribute name="target"/>
                <sequential>
                    <subant target="@{target}">
                        <fileset dir="." includes="*/build.xml"/>
                    </subant>
                </sequential>
            </macrodef>

            <target name="dist">
                <iterate target="dist"/>
            </target>

            <target name="compile">
                <iterate target="compile"/>
            </target>

            <target name="clean">
                <iterate target="clean"/>
            </target>
</project>

This presumes all sub projects have a compile, clean, and dist target. I may add a test target as well.