Plugin_Upgrader::bulk_upgrade()

	public function bulk_upgrade( $plugins, $args = array() ) {
		$defaults    = array(
			'clear_update_cache' => true,
		);
		$parsed_args = gc_parse_args( $args, $defaults );

		$this->init();
		$this->bulk = true;
		$this->upgrade_strings();

		$current = get_site_transient( 'update_plugins' );

		add_filter( 'upgrader_clear_destination', array( $this, 'delete_old_plugin' ), 10, 4 );

		$this->skin->header();

		// Connect to the filesystem first.
		$res = $this->fs_connect( array( GC_CONTENT_DIR, GC_PLUGIN_DIR ) );
		if ( ! $res ) {
			$this->skin->footer();
			return false;
		}

		$this->skin->bulk_header();

		/*
		 * Only start maintenance mode if:
		 * - running Multisite and there are one or more plugins specified, OR
		 * - a plugin with an update available is currently active.
		 * @todo For multisite, maintenance mode should only kick in for individual sites if at all possible.
		 */
		$maintenance = ( is_multisite() && ! empty( $plugins ) );
		foreach ( $plugins as $plugin ) {
			$maintenance = $maintenance || ( is_plugin_active( $plugin ) && isset( $current->response[ $plugin ] ) );
		}
		if ( $maintenance ) {
			$this->maintenance_mode( true );
		}

		$results = array();

		$this->update_count   = count( $plugins );
		$this->update_current = 0;
		foreach ( $plugins as $plugin ) {
			$this->update_current++;
			$this->skin->plugin_info = get_plugin_data( GC_PLUGIN_DIR . '/' . $plugin, false, true );

			if ( ! isset( $current->response[ $plugin ] ) ) {
				$this->skin->set_result( 'up_to_date' );
				$this->skin->before();
				$this->skin->feedback( 'up_to_date' );
				$this->skin->after();
				$results[ $plugin ] = true;
				continue;
			}

			// Get the URL to the zip file.
			$r = $current->response[ $plugin ];

			$this->skin->plugin_active = is_plugin_active( $plugin );

			$result = $this->run(
				array(
					'package'           => $r->package,
					'destination'       => GC_PLUGIN_DIR,
					'clear_destination' => true,
					'clear_working'     => true,
					'is_multi'          => true,
					'hook_extra'        => array(
						'plugin' => $plugin,
					),
				)
			);

			$results[ $plugin ] = $this->result;

			// Prevent credentials auth screen from displaying multiple times.
			if ( false === $result ) {
				break;
			}
		} // End foreach $plugins.

		$this->maintenance_mode( false );

		// Force refresh of plugin update information.
		gc_clean_plugins_cache( $parsed_args['clear_update_cache'] );

		/** This action is documented in gc-admin/includes/class-gc-upgrader.php */
		do_action(
			'upgrader_process_complete',
			$this,
			array(
				'action'  => 'update',
				'type'    => 'plugin',
				'bulk'    => true,
				'plugins' => $plugins,
			)
		);

		$this->skin->bulk_footer();

		$this->skin->footer();

		// Cleanup our hooks, in case something else does a upgrade on this connection.
		remove_filter( 'upgrader_clear_destination', array( $this, 'delete_old_plugin' ) );

		// Ensure any future auto-update failures trigger a failure email by removing
		// the last failure notification from the list when plugins update successfully.
		$past_failure_emails = get_option( 'auto_plugin_theme_update_emails', array() );

		foreach ( $results as $plugin => $result ) {
			// Maintain last failure notification when plugins failed to update manually.
			if ( ! $result || is_gc_error( $result ) || ! isset( $past_failure_emails[ $plugin ] ) ) {
				continue;
			}

			unset( $past_failure_emails[ $plugin ] );
		}

		update_option( 'auto_plugin_theme_update_emails', $past_failure_emails );

		return $results;
	}