<?php
// Only in Test and Live Environments...
if ( in_array( $_ENV['PANTHEON_ENVIRONMENT'], Array('test', 'live') ) ) {
  //
  // Disable Core Updates EVERYWHERE (use git upstream)
  //
  add_filter( 'pre_site_transient_update_core', create_function( '$a', "return null;" ) );

  //
  // Disable Plugin Updates
  //
  add_action('admin_menu','hide_admin_notices');
  function hide_admin_notices() {
    remove_action( 'admin_notices', 'update_nag', 3 );
  }

  remove_action( 'load-update-core.php', 'wp_update_plugins' );
  add_filter( 'pre_site_transient_update_plugins', create_function( '$a', "return null;" ) );

  //
  // Disable Theme Updates
  //
  remove_action( 'load-update-core.php', 'wp_update_themes' );
  add_filter( 'pre_site_transient_update_themes', create_function( '$a', "return null;" ) );
}


<?php
// Only in Test and Live Environments...
if ( in_array( $_ENV['PANTHEON_ENVIRONMENT'], Array('test', 'live') ) ) {
  //
  // Disable Core Updates EVERYWHERE (use git upstream)
  //
  function _pantheon_disable_wp_updates() {
    include ABSPATH . WPINC . '/version.php';
    return (object) array(
	    'updates' => array(),
	    'version_checked' => $wp_version,
	    'last_checked' => time(),
    );
  }

  add_filter( 'pre_site_transient_update_core', '_pantheon_disable_wp_updates' );

  //
  // Disable Plugin Updates
  //
  add_action('admin_menu','hide_admin_notices');
  function hide_admin_notices() {
    remove_action( 'admin_notices', 'update_nag', 3 );
  }

  remove_action( 'load-update-core.php', 'wp_update_plugins' );
  add_filter( 'pre_site_transient_update_plugins', '_pantheon_disable_wp_updates' );

  //
  // Disable Theme Updates
  //
  remove_action( 'load-update-core.php', 'wp_update_themes' );
  add_filter( 'pre_site_transient_update_themes', '_pantheon_disable_wp_updates' );
}


Fix bug with how Pantheon is disabling updates
Fix bug with how Pantheon is disabling updates