gentoo-overlay/app-misc/unfoo/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
  <herd>shell-tools</herd>
  <use>
    <flag name="minimal">Do not install all support archive binaries</flag>
  </use>
  <upstream>
    <remote-id type="github">jlec/unfoo</remote-id>
  </upstream>
</pkgmetadata>