src/vs/workbench/services/userDataSync/browser/userDataSyncWorkbenchService.ts/UserDataSyncPreview/apply
class UserDataSyncPreview:	async apply(): Promise<void> {
		if (!this.manualSync) {
			throw new Error('Can apply only while syncing manually');
		}

		try {
			const syncPreview = await this.manualSync.task.apply();
			this.updatePreview(syncPreview);
			if (!this._resources.length) {
				this._onDidCompleteManualSync.fire(undefined);
			}
		} catch (error) {
			await this.manualSync.task.stop();
			this.updatePreview([]);
			this._onDidCompleteManualSync.fire(error);
		}
	}