src/vs/workbench/services/extensions/common/workspaceContains.ts/_activateIfFileName
async function _activateIfFileName(host: IExtensionActivationHost, fileName: string, activate: (activationEvent: string) => void): Promise<void> {
	// find exact path
	for (const uri of host.folders) {
		if (await host.exists(resources.joinPath(URI.revive(uri), fileName))) {
			// the file was found
			activate(`workspaceContains:${fileName}`);
			return;
		}
	}
}