src/vs/workbench/services/themes/browser/fileIconThemeData.ts/handleParentFolder
function handleParentFolder(key: string, selectors: string[]): string {
	const lastIndexOfSlash = key.lastIndexOf('/');
	if (lastIndexOfSlash >= 0) {
		const parentFolder = key.substring(0, lastIndexOfSlash);
		selectors.push(`.${escapeCSS(parentFolder)}-name-dir-icon`);
		return key.substring(lastIndexOfSlash + 1);
	}
	return key;
}