ManageWP: Update must use plugin from S3

managewp-update-mu-plugin-from-s3.php

<?php
function update_myplugin() {
    // Get current version number
    require_once ABSPATH . 'wp-admin/includes/plugin.php';
    $version = get_plugin_data(WPMU_PLUGIN_DIR .'/myplugin.php');
    
    // Check if current version is latest
	if($version['Version'] < 1.0) {
		// Use wp_remote_get to fetch the data and store it to a file
		$response = wp_remote_get('https://s3.amazonaws.com/path/to/zipfile/myplugin.zip', array( 'stream' => true, 'filename' => WPMU_PLUGIN_DIR . '/myplugin.zip') );

		// Create the name of the file and the declare the directory and path
		$file = WPMU_PLUGIN_DIR . '/myplugin.zip';

		// Require the filesystem API class
		require_once(ABSPATH .'/wp-admin/includes/file.php');
		
		// Make sure we have permissions
		$creds = request_filesystem_credentials(site_url() . '/wp-admin/', '', false, false, array());

		// Initialize the filesystem API
		if ( ! WP_Filesystem($creds) ) {
			/* any problems and we exit */
			return false;
		}	

		global $wp_filesystem;

		// Remove old plugin directory
		$remove_old_plugin = $wp_filesystem->rmdir( WPMU_PLUGIN_DIR . '/myplugin', true );

		if($remove_old_plugin  !== true) {
			/* remove failed. handle error */
			echo "Failed to remove old directory\r\n";
		} else {
			echo "Old directory removed\r\n";

			// Delete loader mu-plugins/myplugin.php file
			$delete_loader = $wp_filesystem->delete( WPMU_PLUGIN_DIR . '/myplugin.php' );
		}

		// Make sure path is correct
		$plugin_path = str_replace(ABSPATH, $wp_filesystem->abspath(), WPMU_PLUGIN_DIR);
		
		// Unzip file
		$unzip = unzip_file($file, $plugin_path); 

		if($unzip !== true) {
			/* unzip failed. Handle Error */
			echo "Failed to unzip file\r\n";
		} else {
			echo "Plugin updated successfully\r\n";
			
			// Move loader myplugin.php file to mu-plugin root
			$move_myplugin = $wp_filesystem->move( WPMU_PLUGIN_DIR . '/myplugin/myplugin.php', WPMU_PLUGIN_DIR . '/myplugin.php' );
		}

		// Delete zip file
		$delete_zip = $wp_filesystem->delete( $file );
		
		// Delete loader myplugin.php from inside myplugin folder
		$delete_loader = $wp_filesystem->delete( WPMU_PLUGIN_DIR . '/myplugin/myplugin.php' );
		
		return $unzip;
	} else {
		echo 'Plugin is at latest version';
		return false;
	}

}

update_myplugin();