dev-libs/libtermkey/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
  <herd>vim</herd>
  <use>
    <flag name='demos'>Install demos, which pulls in <pkg>dev-libs/glib</pkg></flag>
  </use>
</pkgmetadata>