protected function append_theme_actions_content( $theme ) {
		$details_url       = esc_attr(
			add_query_arg(
				[
					'tab'       => 'theme-information',
					'theme'     => $theme->slug,
					'TB_iframe' => 'true',
					'width'     => 270,
					'height'    => 400,
				],
				self_admin_url( 'theme-install.php' )
			)
		);
		$nonced_update_url = wp_nonce_url(
			$this->get_update_url( 'theme', 'upgrade-theme', $theme->slug ),
			'upgrade-theme_' . $theme->slug
		);

		$current = get_site_transient( 'update_themes' );

		/**
		 * Display theme update links.
		 */
		ob_start();
		if ( isset( $current->response[ $theme->slug ] ) ) {
			?>
			<p>
				<strong>
					<?php
					printf(
						/* translators: %s: theme name */
						esc_html__( 'There is a new version of %s available.', 'github-updater' ),
						$theme->name
					);
					printf(
						' <a href="%s" class="thickbox open-plugin-details-modal" title="%s">',
						$details_url,
						esc_attr( $theme->name )
					);
					printf(
						/* translators: 1: version number, 2: closing anchor tag, 3: update URL */
						esc_html__( 'View version %1$s details%2$s or %3$supdate now%2$s.', 'github-updater' ),
						$theme->remote_version = isset( $theme->remote_version ) ? $theme->remote_version : null,
						'</a>',
						sprintf(
							/* translators: %s: theme name */
							'<a aria-label="' . esc_html__( 'Update %s now', 'github-updater' ) . '" id="update-theme" data-slug="' . $theme->slug . '" href="' . $nonced_update_url . '">',
							$theme->name
						)
					);
					?>
				</strong>
			</p>
			<?php
		}

		return trim( ob_get_clean(), '1' );
	}