gitignore modification doesn't work

Record the problems and solutions encountered
http://blog.csdn.net/cloudspider/article/details/53463687

In the process of using git, I sometimes encounter the modification of the .gitignore file. After modification, it is found that it does not work. This is because git has a cache problem, so do the following steps:

git rm -r –cached .
git add .
git commit -m “update gitignore”