定义自定义配置文件路径

```
(custom-set-variables
 ;; custom-set-variables was added by Custom.
 ;; If you edit it by hand, you could mess it up, so be careful.
 ;; Your init file should contain only one such instance.
 ;; If there is more than one, they won't work right.
 '(custom-safe-themes (quote ("4aee8551b53a43a883cb0b7f3255d6859d766b6c5e14bcb01bed572fcbef4328" default))))
(custom-set-faces
 ;; custom-set-faces was added by Custom.
 ;; If you edit it by hand, you could mess it up, so be careful.
 ;; Your init file should contain only one such instance.
 ;; If there is more than one, they won't work right.
 )
```

像上面那样的代码是emacs自动生成的代码，同样，通过M-x customize自定义的配置也会生成一些配置代码。

加上以下两行配置
```
(setq custom-file "~/.emacs.d/custom.el")
(load custom-file)
```

可以让所有由emacs生成的配置都写进 ~/.emacs.d/custom.el这个文件，而不会弄乱init.el这个文件里面的配置。