From http://stackoverflow.com/questions/4344139/how-to-get-a-return-value-from-an-exec-in-ant-script failoneerror from exectable call example - used for our git commands

fail_on_errror_exec

<target name="CheckState">
     <exec executable="${App.path}"
           resultproperty="App.state"
           failonerror="false"/>
     <echo message="App state was: ${App.state}" />
</target>