On Ubuntu 14.04, cat can display Chinese characters correctly.
But in vi and less Chinese characters can't display correctly.
Solution:
Run export LC_ALL=en_US.UTF-8 before git log.
If it works, add this line into /etc/environment.
If it doesn't work, run export LANG=en_US.UTF-8.
If it doesn't work, run apt-get install language-pack-en-base.
In vim, run set enc=utf-8.
Ref:
http://askubuntu.com/questions/162391/how-do-i-fix-my-locale-issue
http://stackoverflow.com/questions/5166652/how-to-view-utf-8-characters-in-vim-or-gvim