repo sync后，repo已自动修改

Question

在macosx上，我使用以下命令从google重新同步：

repo init -u https://android.googlesource.com/platform/manifest -b android-8.0.0_r4
repo sync frameworks/av

然后在frameworks / av中，我发现一个文件总是被修改：

cd frameworks/av/
git status
Not currently on any branch.
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)

    modified:   media/libstagefright/include/DataURISource.h

no changes added to commit (use "git add" and/or "git commit -a")

我根本无法删除该修改过的文件，git reset --hard无效。