<?php
/**
 * Remove the slug from published post permalinks. Only affect our CPT though.
 */
function wpex_remove_cpt_slug( $post_link, $post, $leavename ) {
	if ( 'portfolio' != $post->post_type || 'publish' != $post->post_status ) {
		return $post_link;
	}
	$post_link = str_replace( '/' . $post->post_type . '/', '/', $post_link );
	return $post_link;
}
add_filter( 'post_type_link', 'wpex_remove_cpt_slug', 10, 3 );


/**
 * Some hackery to have WordPress match postname to any of our public post types
 * All of our public post types can have /post-name/ as the slug, so they better be unique across all posts
 * Typically core only accounts for posts and pages where the slug is /post-name/
 */
function wpex_parse_request_tricksy( $query ) {
	// Only noop the main query
	if ( ! $query->is_main_query() )
		return;
	// Only noop our very specific rewrite rule match
	if ( 2 != count( $query->query ) || ! isset( $query->query['page'] ) ) {
		return;
	}
	// 'name' will be set if post permalinks are just post_name, otherwise the page rule will match
	if ( ! empty( $query->query['name'] ) ) {
		$query->set( 'post_type', array( 'post', 'portfolio', 'page' ) );
	}
}
add_action( 'pre_get_posts', 'wpex_parse_request_tricksy' );