Wordpress filter to convert copied Markdown

wp-content-filter-gh

/* ----- change content on output as needed                                      ----- */  
function stripFirstLine( $text ) {
	// removes first line of text from string
	// ----- h/t http://stackoverflow.com/a/7740485/2418186
	return substr( $text, strpos($text, "\n")+1 );
}
add_filter( 'the_content', 'cc_cert_content_filter', 20 );
function cc_cert_content_filter( $content ) {
	if ( is_page_template( 'page-cert.php' ) ) {
	
		// replace local links in markdown tp work as sub page links in WP
		$content = str_replace ( '.md', '/', $content);
	
		// replace all URLs for the repo image with one for GH pages (so we can link)
		$content = str_replace ( 'https://github.com/creativecommons/cc-cert-map/blob/master/img/' , 'https://creativecommons.github.io/cc-cert-map/img/' , $content);
		
		$content = do_shortcode('[siblings depth="1" class="topnav"]') . $content;
	
   } elseif ( is_page_template( 'page-map.php' ) ) {
        // remove first line that has # Header)
		$content = stripFirstLine( $content );
		
		// replace all URLs for the repo image with one for GH pages (so we can link)
		$content = str_replace ( 'https://github.com/creativecommons/cc-cert-map/blob/master/img/' , 'https://creativecommons.github.io/cc-cert-map/img/' , $content);
		
		// set up shortcode stuff to prefix content, based on parent ID
		$parent_id = wp_get_post_parent_id( get_the_ID() );
		
		// insert short codes
		$content = do_shortcode('[pagelist child_of="' . wp_get_post_parent_id($parent_id) . '" depth="1" class="topnav"]') . do_shortcode('[modnav title="' . get_the_title($parent_id)  . '" type="module"]') . $content;
		
	}
	
    // Send back the content, pronto!
    return $content;
}