private static function load_yml( $yml_file ) {
		if ( ! $yml_file ) {
			return array();
		}

		$config = Spyc::YAMLLoad( $yml_file );

		// Make sure config-file-relative paths are made absolute.
		$yml_file_dir = dirname( $yml_file );

		if ( isset( $config['path'] ) ) {
			self::absolutize( $config['path'], $yml_file_dir );
		}

		if ( isset( $config['require'] ) ) {
			self::arrayify( $config['require'] );
			$config['require'] = \WP_CLI\Utils\expand_globs( $config['require'] );
			foreach ( $config['require'] as &$path ) {
				self::absolutize( $path, $yml_file_dir );
			}
		}

		// Backwards compat
		// Command 'core config' was moved to 'config create'.
		if ( isset( $config['core config'] ) ) {
			$config['config create'] = $config['core config'];
			unset( $config['core config'] );
		}
		// Command 'checksum core' was moved to 'core verify-checksums'.
		if ( isset( $config['checksum core'] ) ) {
			$config['core verify-checksums'] = $config['checksum core'];
			unset( $config['checksum core'] );
		}
		// Command 'checksum plugin' was moved to 'plugin verify-checksums'.
		if ( isset( $config['checksum plugin'] ) ) {
			$config['plugin verify-checksums'] = $config['checksum plugin'];
			unset( $config['checksum plugin'] );
		}

		return $config;
	}