git remove submodule

最保险删除submodule的方法:(转自Stack Overflow)
Via the page Git Submodule Tutorial:To remove a submodule you need to:

    Delete the relevant section from the .gitmodules file.
    Stage the .gitmodules changes:
    git add .gitmodules
    Delete the relevant section from .git/config.
    Remove the submodule files from the index:
    git rm --cached path_to_submodule (no trailing slash).
    Remove the submodule's .git directory:
    rm -rf .git/modules/path_to_submodule
    Commit the changes:
    git commit -m "Removed submodule <name>"
    Delete the now untracked submodule files:
    rm -rf path_to_submodule