Ticket #17347: trac-links.php

<?php
/*
Plugin Name: Trac Links
Plugin URI: http://wordpress.org/
Description: Link ticket and changeset numbers to core.trac.wordpress.org
Version: 1.0.1
Author: Automattic
Author URI: http://wordpress.org/
*/

add_filter( 'the_content', 'markup_wporg_links', 10, 1 );
add_filter( 'comment_text', 'markup_wporg_links', 10, 1 );

function markup_wporg_links( $content ) {
        $find = array(
                '/[\b]?#(\d{3,6})[\b]?/i', // core trac ticket #1234 in http://core.trac.wordpress.org/ticket/1234
                '/[\b]?r(\d{3,6})[\b]?/i', // core changeset r1234 in http://core.trac.wordpress.org/changeset/1234
                '/[\b]?diff:@(\d{3,6}):(\d{3,6})[\b]?/i', // core diff diff:@200:300 https://core.trac.wordpress.org/changeset?new=300&old=200
        );

        $replace = array(
                '<a href="http://core.trac.wordpress.org/ticket/$1">$0</a>', // core trac ticket
                '<a href="http://core.trac.wordpress.org/changeset/$1">$0</a>', // core trac changeset
                '<a href="http://core.trac.wordpress.org/changeset?new=$2&old=$1">$0</a>', // core diff
        );

        preg_match_all( '#[^>]+(?=<[^/]*[^a])|[^>]+$#', $content, $matches, PREG_SET_ORDER );

        foreach ( $matches as $match ) {
                $content = str_replace( $match[0], preg_replace( $find, $replace, $match[0] ), $content );
        }

        return $content;
}