Even if you haven't tracked the files so far, git seems to be able to "know" about them even after you add them to .gitignore.
NOTE : First commit your current changes, or you will lose them.
Then run the following commands from the top folder of your git repo:
git rm -r --cached .
git add .
git commit -m "fixed untracked files"
也可以做成脚本，在项目根目录下执行。（记得先把本地代码提交）
#!/bin/sh
git rm -r --cached .
git add .
git commit -m "fixed untracked files"
