今天提交代码出现以下现象：

admin:ios-hybird-flutter Red$ git add .
admin:ios-hybird-flutter Red$ git st
On branch master
Your branch is up to date with 'origin/master'.

Changes to be committed:
  (use "git restore --staged <file>..." to unstage)
    new file:   FlutterBoostDemo/.gitignore
    new file:   FlutterBoostDemo/.metadata
    new file:   FlutterBoostDemo/FlutterBoostDemo.iml
    new file:   FlutterBoostDemo/FlutterBoostDemo_android.iml
    new file:   FlutterBoostDemo/README.md
    new file:   FlutterBoostDemo/lib/FirstPage.dart
    new file:   FlutterBoostDemo/lib/main.dart
    new file:   FlutterBoostDemo/pubspec.lock
    new file:   FlutterBoostDemo/pubspec.yaml
    new file:   FlutterBoostDemo/test/widget_test.dart
    new file:   SwiftDemo

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)
  (commit or discard the untracked or modified content in submodules)
    modified:   SwiftDemo (modified content, untracked content)

问题：

modified:   SwiftDemo (modified content, untracked content)

SwiftDemo目录没有被跟踪，尝试几次都没有add上去，从SourceTree上看SwiftDemo只是一个空目录，目录下的文件没有加进去。

解决办法：
SwiftDemo目录里有一个.git目录，就是说SwiftDemo本身也是一个代码库。

admin:SwiftDemo Red$ rm -rf .git

删除.git目录后，git add . 还是不行。

最后把SwiftDemo目录移动到其它目录，再移回去，git add . 正常。