gentoo-overlay/app-portage/conf-update/metadata.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE pkgmetadata SYSTEM "http://www.gentoo.org/dtd/metadata.dtd">
<pkgmetadata>
	<!-- maintainer-needed -->
	<use>
		<flag name="colordiff">Use colors when displaying diffs (<pkg>app-misc/colordiff</pkg>)</flag>
		<flag name="libressl">Enable SSL connections and crypto functions using <pkg>dev-libs/libressl</pkg></flag>
	</use>
</pkgmetadata>