command-line window of vim就是把vim在:模式下输入的命令列出来的窗口，当你保存文件时，按错键，会进入该窗口；

下面两种方法会进入该窗口：
There are two ways to open the command-line window:
1. From Command-line mode, use the key specified with the ‘cedit’ option.
The default is CTRL-F when ‘compatible’ is not set.
2. From Normal mode, use the “q:”, “q/“ or “q?” command.
This starts editing an Ex command-line (“q:”) or search string (“q/“ or
“q?”). Note that this is not possible while recording is in progress (the
“q” stops recording then).
如何退出：
把它当成正常的文件输入:q，就可以退出了。