How to Integrate Trac and WordPress (as done on the WP Development blog)?

Here's the source of the functionality. It's just a content filter and some basic regex that one of my coworkers at Automattic wrote.

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

function markup_wporg_links( $content ) {
    $find = array(
        '/(\ |^)#(\d{3,6})(\b|$)/i', // core trac ticket #1234-core in http://core.trac.wordpress.org/ticket/
        '/(\ |^)r(\d{3,6})(\b|$)/i', // core changeset r1234-core in http://core.trac.wordpress.org/changeset/1234
        '/(\ |^)diff:@(\d{3,6}):(\d{3,6})(\b|$)/i', // core diff diff-core:@20:30 https://core.trac.wordpress.org/changeset?new=30&old=20
    );

    $replace = array(
        '<a href="http://core.trac.wordpress.org/ticket/$2">$0</a>', // core trac ticket
        '<a href="http://core.trac.wordpress.org/changeset/$2">$0</a>', // core trac changeset
        '<a href="http://core.trac.wordpress.org/changeset?new=$3&old=$2">$0</a>', // core diff
    );

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

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

    return $content;
}

Modify it to suit your needs.

Also take a look at RTC (free for 10 users on jazz.net) it is the next big thing.

It automatically combines changing your stuff with the work items attached / diffs / with even your planning. It's the followup of Eclipse (which provided an open source framework).

IMHO the best thing out there currently