使用.gitignore文件删除掉已经提交的文件
 
顺序依次执行如下命令：

First commit any outstanding code changes, and then, run this command:

git rm -r --cached .
This removes any changed files from the index(staging area), then just run:

git add .
Commit it:

git commit -m ".gitignore is now working"
最后提交到远程仓库，会发现.gitignore文件起作用了。