切换分支时 git clean 不会删除添加到分支的子模块

切换分支时如何摆脱子模块。我不明白为什么 git clean 说它删除了子模块但没有。这是一个错误吗？以下是复制的剪切和粘贴步骤。

git --version
git version 1.7.8.4

git init submod
cd submod
echo "This is a submodule" > README.txt
git add .
git commit -m "Initial commit"
cd ..
git init prog
cd prog
echo "This is a program" > README.txt
git add .
git commit -a -m "Initial commit"
git checkout -b topic1
git submodule add ../submod
git commit -m "Added submodule"

git checkout master
#warning: unable to rmdir submod: Directory not empty
#Switched to branch 'master'

git status
# On branch master
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#       submod/
#nothing added to commit but untracked files present (use "git add" to track)

git clean -fd
#Removing submod/

git status
# On branch master
# Untracked files:
#   (use "git add <file>..." to include in what will be committed)
#
#       submod/
#nothing added to commit but untracked files present (use "git add" to track)

这不是错误，而是已记录的行为。从man git-clean:

如果未跟踪的目录由不同的 git 存储库管理，则默认情况下不会将其删除。

The submod目录不同git存储库；如果你想删除它，Use -f option twice if you really want to remove such a directory.

git clean -f -f -d submod does remove submod。请参阅下面的我的步骤（几乎相同；不同git version和硬编码的submodule路径，因为否则git假人吐口水）。

Steps

$ git --version
git version 1.7.5.4 # Note, different git-version. 

制作两个存储库

git init submod
cd submod
echo "This is a submodule" > README.txt
git add .
git commit -m "Initial commit"
cd ..
git init prog
cd prog
echo "This is a program" > README.txt
git add .
git commit -a -m "Initial commit"

Add submod as a git submodule in topic1 branch.

git checkout -b topic1
git submodule add /Users/simont/sandbox/SOTESTING/Subdir-testing/submod
git commit -m "Added submodule"

现在是有趣的部分。

$ git checkout master
warning: unable to rmdir submod: Directory not empty
Switched to branch 'master'

git status
# On branch master
# Untracked files:
#   (use "git add ..." to include in what will be committed)
#
#       submod/
#nothing added to commit but untracked files present (use "git add" to track)

尝试git-clean, then actually git-clean.

git clean -fd
#Removing submod/

git status
# On branch master
# Untracked files:
#   (use "git add ..." to include in what will be committed)
#
#       submod/
#nothing added to commit but untracked files present (use "git add" to track)

$ # As we can see, we haven't actually removed anything yet. 
$ ls
README.txt  submod

$ git clean -f -f -d submod
Removing submod/

$ ls
README.txt

$ git status
# On branch master
nothing to commit (working directory clean)