src/vs/platform/userDataSync/common/abstractSynchronizer.ts/AbstractSynchroniser/apply
class AbstractSynchroniser:	async apply(force: boolean, headers: IHeaders = {}): Promise<ISyncResourcePreview | null> {
		try {
			this.syncHeaders = { ...headers };

			const status = await this.doApply(force);
			this.setStatus(status);

			return this.syncPreviewPromise;
		} finally {
			this.syncHeaders = {};
		}
	}