WordPress theme stylesheet auto cache-busting

constant.php

<?php

define( 'MY_THEME_VERSION', '1.4' );

/**
 * Enqueue stylesheet
 *
 * Uses a constant that has to be manually updated
 */
function my_theme_enqueue_assets() {
    wp_enqueue_style( 'stylesheet', get_stylesheet_uri(), array(), MY_THEME_VERSION );
    // stylesheet URL: https://mydomain.com/wp-content/themes/my-theme/style.css?ver=1.4
}
add_action( 'wp_enqueue_scripts', 'my_theme_enqueue_assets' );

filemtime-filename.php

<?php

/**
 * Enqueue stylesheet
 *
 * Uses the modification timestamp of the style.css file
 */
function my_theme_enqueue_assets() {
    wp_enqueue_style( 'stylesheet', str_replace( '.css', '.' . filemtime( get_stylesheet_directory() . '/style.css' ) . '.css', get_stylesheet_uri() ) );
    // stylesheet URL: https://mydomain.com/wp-content/themes/my-theme/style.1518212243.css
}
add_action( 'wp_enqueue_scripts', 'my_theme_enqueue_assets' );
  

filemtime.php

<?php

/**
 * Enqueue stylesheet
 *
 * Uses the modification timestamp of the style.css file
 */
function my_theme_enqueue_assets() {
    wp_enqueue_style( 'stylesheet', get_stylesheet_uri(), array(), filemtime( get_stylesheet_directory() . '/style.css' ) );
    // stylesheet URL: https://mydomain.com/wp-content/themes/my-theme/style.css?ver=1518212243
}
add_action( 'wp_enqueue_scripts', 'my_theme_enqueue_assets' );

style.css

/**
 * Theme Name: Twenty Seventeen
 * Theme URI: https://wordpress.org/themes/twentyseventeen/
 * Author: the WordPress team
 * Author URI: https://wordpress.org/
 * Description: Twenty Seventeen brings your site to life with header video and immersive featured images. With a focus on business sites, it features multiple sections on the front page as well as widgets, navigation and social menus, a logo, and more. Personalize its asymmetrical grid with a custom color scheme and showcase your multimedia content with post formats. Our default theme for 2017 works great in many languages, for any abilities, and on any device.
 * Version: 1.4
 * License: GNU General Public License v2 or later
 * License URI: http://www.gnu.org/licenses/gpl-2.0.html
 * Text Domain: twentyseventeen
 * Tags: one-column, two-columns, right-sidebar, flexible-header, accessibility-ready, custom-colors, custom-header, custom-menu, custom-logo, editor-style, featured-images, footer-widgets, post-formats, rtl-language-support, sticky-post, theme-options, threaded-comments, translation-ready

 * This theme, like WordPress, is licensed under the GPL.
 * Use it to make something cool, have fun, and share what you've learned with others.
 */

// or at the very least:

/**
 * Theme Name: Twenty Seventeen
 * Version: 1.4
 */

WP-theme-version-filename.php

<?php

/**
 * Autocalculate and define theme version constant for use in multiple stylesheets/scripts
 */
define( 'MY_THEME_VERSION', wp_get_theme()->get( 'Version' ) );

/**
 * Enqueue stylesheet
 *
 * Uses the Version header from style.css
 */
function my_theme_enqueue_assets() {
    wp_enqueue_style( 'stylesheet', str_replace( '.css', '.' . MY_THEME_VERSION . '.css', get_stylesheet_uri() ) );
    // stylesheet URL: https://mydomain.com/wp-content/themes/my-theme/style.1.4.css
}
add_action( 'wp_enqueue_scripts', 'my_theme_enqueue_assets' );

WP-theme-version.php

<?php

/**
 * Auto-calculate and define theme version constant for use in multiple stylesheets/scripts
 */
define( 'MY_THEME_VERSION', wp_get_theme()->get( 'Version' ) );

/**
 * Enqueue stylesheet
 *
 * Uses the Version header from style.css
 */
function my_theme_enqueue_assets() {
    wp_enqueue_style( 'stylesheet', get_stylesheet_uri(), array(), MY_THEME_VERSION );
    // stylesheet URL: https://mydomain.com/wp-content/themes/my-theme/style.css?ver=1.4
}
add_action( 'wp_enqueue_scripts', 'my_theme_enqueue_assets' );