我正在使用WinCvs，我在CVSRoot中设置了admin->Login并且能够成功登录。我也在env变量中设置了CVSRoot。我可以使用folder->checkout模块结帐模块，但我无法update文件或查看diff。我收到错误"cvs diff: No CVSROOT specified! Please use the - d'选项，cvs [diff aborted]：或设置CVSROOT环境变量。“I am not able to understand what I am doing wrong. I have already setted CVSRoot` here。