git add .
warning: adding embedded git repository: ppa_frontend
hint: You’ve added another git repository inside your current repository.
hint: Clones of the outer repository will not contain the contents of
hint:
hint: git submodule add ppa_frontend
hint:
hint: If you added this path by mistake, you can remove it from the
hint:
hint: git rm --cached ppa_frontend
hint:
按照提示輸入

 git rm --cached ppa_frontend

即可重新git add .