<propertyset> and <property> for <hibernatetool> and <hbm2....> exporters which allow you to give the templates access to extra properties.
e.g.
<hibernatetool destdir="${build.dir}/bottomup">
<configuration/>
<hbm2java generics="true">
<propertyset>
<propertyref builtin="all"/>
<propertyref name="hbm2java.ejb3"/>
<propertyref prefix="hbm2java"/>
</propertyset>
<property key="mykey" file="c"/>
<property key="mykey" value="c"/>
</hbm2java>
</hibernatetool>

document support for having custom variables point to an instance via these properties.

sometool.toolclass=NameOfClass will be available as $sometool referencing an instance of NameOfClass

In theory all settings should be property driven (generics,ejb3,prefercompositeids, etc.), but need to ensure that it actually works in practice