src/vs/platform/userDataSync/common/settingsMerge.ts/getIgnoredSettings
export function getIgnoredSettings(defaultIgnoredSettings: string[], configurationService: IConfigurationService, settingsContent?: string): string[] {
	let value: ReadonlyArray<string> = [];
	if (settingsContent) {
		value = getIgnoredSettingsFromContent(settingsContent);
	} else {
		value = getIgnoredSettingsFromConfig(configurationService);
	}
	const added: string[] = [], removed: string[] = [...getDisallowedIgnoredSettings()];
	if (Array.isArray(value)) {
		for (const key of value) {
			if (key.startsWith('-')) {
				removed.push(key.substring(1));
			} else {
				added.push(key);
			}
		}
	}
	return distinct([...defaultIgnoredSettings, ...added,].filter(setting => removed.indexOf(setting) === -1));
}