From: http://leloup.blog.51cto.com/blog/1113857/596107
在vim的官方FAQ （http://vimdoc.sourceforge.net/cgi-bin/vimfaq2html3.pl#14.6）找到的：
格式化全文： gg=G
自动缩进当前行： ==
这个是原文节选：
14.6. How do I format/indent an entire file?
You can format/indent an entire file using the gg=G command, where
gg - Goto the beginning of the file
= - apply indentation
G - till end of file
For more information, read
:help gg
:help =
:help G
:help 'formatprg'
:help C-indenting