src/vs/code/node/cliProcessMain.ts/CliMain/setInstallSource
class CliMain:	private async setInstallSource(environmentService: INativeEnvironmentService, fileService: IFileService, installSource: string): Promise<void> {
		await fileService.writeFile(URI.file(environmentService.installSourcePath), VSBuffer.fromString(installSource.slice(0, 30)));
	}