Git提交或者添加时，提示index.lock文件存在，无法提交或者添加
解决办法一：
On linux/unix/gitbash/cygwin, try：
rm -f .git/index.lock
On Windows Command Prompt, try:
de >del .git\index.lock de>
解决办法二：
de >de>
Go to: Tools > Options > Source Control
Select Current source control plug-in as: None
解决办法三：
check if the git still running (ps -ef | grep git)
if not, remove the locked file
if yes, kill the git process at first.
