gentoo-overlay/dev-libs/libzypp/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
  <herd>suse</herd>
  <use>
    <flag name="libproxy">Use <pkg>net-libs/libproxy</pkg> for getting the HTTP/HTTPS/SOCKS proxy configuration</flag>
  </use>
</pkgmetadata>