src/vs/platform/files/common/watcher.ts/normalizeWatcherPattern
export function normalizeWatcherPattern(path: string, pattern: string | IRelativePattern): string | IRelativePattern {

	// Patterns are always matched on the full absolute path
	// of the event. As such, if the pattern is not absolute
	// and is a string and does not start with a leading
	// `**`, we have to convert it to a relative pattern with
	// the given `base`

	if (typeof pattern === 'string' && !pattern.startsWith(GLOBSTAR) && !isAbsolute(pattern)) {
		return { base: path, pattern };
	}

	return pattern;
}