Documentation for aapt element in Ant script

I'm working on some Ant scripts for an Android build system and have come across an element to call aapt. I have seen lots of examples with

exec executable="${aapt}"

but the ones that come out of the main_rules.xml file use a different format

    <aapt executable="${aapt}"
            command="package"
            debug="${build.packaging.debug}"
            manifest="AndroidManifest.xml"
            assets="${asset.absolute.dir}"
            androidjar="${android.jar}"
            apkfolder="${out.absolute.dir}"
            resourcefilename="${resource.package.file.name}"
            resourcefilter="${aapt.resource.filter}">
        <res path="${resource.absolute.dir}" />
        <!-- <nocompress /> forces no compression on any files in assets or res/raw -->
        <!-- <nocompress extension="xml" /> forces no compression on specific file extensions in assets and res/raw -->
    </aapt>

I would like to rename the package using this element, but cannot find any documentation about how to use it. Does anyone know where I can find some?

Thanks