The exercise-tree utility is licensed under LGPL and can be found at
https://mathdox.org/svn/repos/public/mathdoxutils/exercise-tree
To include:
1) copy the files in this directory to ant/exercise-tree/*
2) edit exercise-tree.properies to change the paths
3) add an tag inside the tag in the main build.xml as below:
4) the new target "exercise-tree" should create exercise-tree.xml files
5) to do this automatically add this to the depends attribute of the default target