src/vs/workbench/contrib/extensions/browser/extensionsWorkbenchService.ts/ExtensionsWorkbenchService/installFromVSIX
class ExtensionsWorkbenchService:	private async installFromVSIX(vsix: URI, installOptions?: InstallVSIXOptions): Promise<IExtension> {
		const manifest = await this.extensionManagementService.getManifest(vsix);
		const existingExtension = this.local.find(local => areSameExtensions(local.identifier, { id: getGalleryExtensionId(manifest.publisher, manifest.name) }));
		const { identifier } = await this.extensionManagementService.install(vsix, installOptions);

		if (existingExtension && existingExtension.latestVersion !== manifest.version) {
			this.ignoreAutoUpdate(new ExtensionKey(identifier, manifest.version));
		}

		return this.local.filter(local => areSameExtensions(local.identifier, identifier))[0];
	}