games-fps/duke3d-data/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
	<herd>games</herd>
	<use>
		<flag name='gog'>Extract the data from the GOG.com installer.</flag>
	</use>
</pkgmetadata>