Ant tasks to check if working directory is clean.

build.xml

<?xml version="1.0" encoding="UTF-8"?>
<project name="git" default="is-working-directory-clean">

    <target name="-git-status">
        <exec executable="git" outputproperty="git.status.message" failifexecutionfails="false" errorproperty="">
            <arg value="status"/>
            <arg value="--short"/>
        </exec>
        <condition property="git.clean.wd">
            <and>
                <equals arg1="${git.status.message}" arg2="" trim="yes"/>
            </and>
        </condition>
    </target>

    <target name="is-working-directory-clean"
            depends="-git-status">
        <fail unless="${git.clean.wd}" message="Working directory is not clean"/>
    </target>

</project>