src/vs/platform/extensionManagement/node/extensionsScanner.ts/ExtensionsScanner/storeMetadata
class ExtensionsScanner:	private async storeMetadata(local: ILocalExtension, storedMetadata: IStoredMetadata): Promise<ILocalExtension> {
		// unset if false
		storedMetadata.isMachineScoped = storedMetadata.isMachineScoped || undefined;
		storedMetadata.isBuiltin = storedMetadata.isBuiltin || undefined;
		storedMetadata.installedTimestamp = storedMetadata.installedTimestamp || undefined;
		const manifestPath = path.join(local.location.fsPath, 'package.json');
		const raw = await pfs.Promises.readFile(manifestPath, 'utf8');
		const { manifest } = await this.parseManifest(raw);
		(manifest as ILocalExtensionManifest).__metadata = storedMetadata;
		await pfs.Promises.writeFile(manifestPath, JSON.stringify(manifest, null, '\t'));
		return local;
	}