gistfile1.php

<?php

// ...<snip>...
<span class="milestone"><# wp.hooks.doAction('milestonerevs.metadata', data) #></span>
// ...<snip>...

add_action( 'admin_footer-revision.php', 'wpse151630_test' );
function wpse151630_test() {
?>
    <script>
    (function($) {
        wp.hooks.addAction('milestonerevs.metadata', function( data ) {
            setTimeout(function(){
                $('.diff-meta-to .milestone').text(data.id);
            }, 100);
        });
    })(jQuery);
    </script>
    <?php
}