Add filter to maintenance_mode() function for $maintenance_string

[amandato]

Please add a filter for the maintenance_mode() function found in includes/class-wp-upgrader.php.

New line:

<?php
...
$maintenance_string = apply_filters( 'maintenance_string', $maintenance_string );
...

Adding this would allow a custom plugin to modify the $maintenance_string. Here is an example where a custom plugin would modify the maintenance string value to allow wp-cli to work while maintaining maintenance mode in all other cases:

<?php
if( !(defined('WP_CLI') && WP_CLI) ) { $upgrading = time(); }

[amandato]

Diff file of change made to WP 4.5.2

[ocean90]

Why would someone want to change that string?

Snippet from wp_maintenance():

global $upgrading;

include( ABSPATH . '.maintenance' );
// If the $upgrading timestamp is older than 10 minutes, don't die.
if ( ( time() - $upgrading ) >= 600 )
	return;

---

class-wp-upgrader.diff​ is a bit broken. The patch should include the full path and the filename. Also, filters need to be documented as per the ​documentation standards.