src/vs/platform/userDataSync/common/extensionsSync.ts/ExtensionsSynchroniser/applyResult
class ExtensionsSynchroniser:	protected async applyResult(remoteUserData: IRemoteUserData, lastSyncUserData: IRemoteUserData | null, resourcePreviews: [IExtensionResourcePreview, IExtensionResourceMergeResult][], force: boolean): Promise<void> {
		let { skippedExtensions, localExtensions } = resourcePreviews[0][0];
		const { local, remote, localChange, remoteChange } = resourcePreviews[0][1];

		if (localChange === Change.None && remoteChange === Change.None) {
			this.logService.info(`${this.syncResourceLogLabel}: No changes found during synchronizing extensions.`);
		}

		if (localChange !== Change.None) {
			await this.backupLocal(JSON.stringify(localExtensions));
			skippedExtensions = await this.updateLocalExtensions(local.added, local.removed, local.updated, skippedExtensions);
		}

		if (remote) {
			// update remote
			this.logService.trace(`${this.syncResourceLogLabel}: Updating remote extensions...`);
			const content = JSON.stringify(remote.all);
			remoteUserData = await this.updateRemoteUserData(content, force ? null : remoteUserData.ref);
			this.logService.info(`${this.syncResourceLogLabel}: Updated remote extensions.${remote.added.length ? ` Added: ${JSON.stringify(remote.added.map(e => e.identifier.id))}.` : ''}${remote.updated.length ? ` Updated: ${JSON.stringify(remote.updated.map(e => e.identifier.id))}.` : ''}${remote.removed.length ? ` Removed: ${JSON.stringify(remote.removed.map(e => e.identifier.id))}.` : ''}`);
		}

		if (lastSyncUserData?.ref !== remoteUserData.ref) {
			// update last sync
			this.logService.trace(`${this.syncResourceLogLabel}: Updating last synchronized extensions...`);
			await this.updateLastSyncUserData(remoteUserData, { skippedExtensions });
			this.logService.info(`${this.syncResourceLogLabel}: Updated last synchronized extensions.${skippedExtensions.length ? ` Skipped: ${JSON.stringify(skippedExtensions.map(e => e.identifier.id))}.` : ''}`);
		}
	}