use wordpress-webmention hook to add rel-syndication links for bridgy publish

functions.php

/** When I POSSE a post with Bridgy Publish, add a rel-syndication URL.
 */
function bridgy_publish_syndication_link($response, $source, $target) {
  $json = json_decode(wp_remote_retrieve_body($response));
  dlog($target);
  dlog($json);
  dlog($response);
  if (!is_wp_error($response) && $json &&
      (strpos($target, 'localhost:8080/publish/facebook') ||
       strpos($target, 'localhost:8080/publish/twitter'))) {
    if ($json->url) {
      $post = get_post(the_ID());
      $post->post_content .=
          "\n" . '<a rel="syndication" class="u-syndication" href="' .
          $json->url . '"></a>';
      wp_insert_post($post);
    }
  }
}
add_action('webmention_post_send', 'bridgy_publish_syndication_link');