如果我在一个父项目分支中更新子模块，然后切换到同一工作树中的另一个分支，子模块引用就会显示为已被修改。
例如（散列可能会有所不同，您可能需要向下滚动代码窗口以查看所有行）：
# create soon to be submodule
mkdir /tmp/example-submodule
cd /tmp/example-submodule
git init
echo a > a
git add a
git commit -m 'm'
cp -r .git /tmp/example-submodule.git
cd /tmp/example-submodule.git
git config --bool core.bare true
cd /tmp
/bin/rm -rf /tmp/example-submodule
git clone file:///tmp/example-submodule.git
#create other project and add sub-module
mkdir /tmp/example-supermodule
cd /tmp/example-supermodule
git init
echo x > x
git add x
git commit -m 'm'
cp -r .git /tmp/example-supermodule.git
cd /tmp/example-supermodule.git
git config --bool core.bare true
cd /tmp
/bin/rm -rf /tmp/example-supermodule
git clone file:///tmp/example-supermodule.git
#update the submodule
cd /tmp/example-supermodule
git submodule add file:///tmp/example-submodule.git example-sub
git commit -a -m'm'
git submodule status
# prints: 189ea25d45618862d0bfcbf5bd995e05ce1c2e4e example-sub (heads/master)
git push
#update the submodule
cd /tmp/example-submodule
echo b > b
git add b
git commit -m 'm'
git push
#create new branch in super module and update submodule to new HEAD
cd /tmp/example-supermodule
git branch otherbranch
git checkout otherbranch
git submodule update --remote
git commit -a -m'm'
git submodule status
# prints: 26f94e59002603475a1ba731104f92e10e88cf6b example-sub (remotes/origin/HEAD)
git push origin otherbranch
#checkout another branch
git checkout master
git status
cat .git/modules/example-sub/HEAD
# prints: 26f94e59002603475a1ba731104f92e10e88cf6b
在签出master之后，子模块的散列不同，就好像otherbranch中的更新也影响了master。
如果我克隆超级项目而不是在同一工作树中切换分支：
cd /tmp
git clone --recursive file:///tmp/example-supermodule.git/ other
cd /tmp/other
git submodule status
它显示了在主分支中添加的子模块提交。
如何有人在其工作树中的分支之间切换，并使子模块的提交与提交的内容相匹配？或者在更改分支后如何恢复显示子模块在该分支中未被修改时被修改？
答案 0 :(得分：1)
我刚用git 2.9.0重现了这个问题
最后你需要做的就是找回干净的主人：
git submodule update
这会将子模块重置为master值，.git/modules/example-sub/HEAD将具有正确的值
再次结帐otherbranch时，您会遇到同样的问题
将检出正确的 gitlink （special entry in the index）
但.git/modules/example-sub/HEAD不会立即更改。
在这两种情况下，这都是因为checkout只修改了gitlink，不是子模块的内容。
只有git submodule update实际上会将子模块的内容检出到其录制的gitlink SHA1。
这样，如果您在子模块中进行了正在进行的工作，那么它们不会被父仓库中的结账消除。
这是我自己的实验：
C:\Users\vonc\prog\git\tests>mkdir subm
C:\Users\vonc\prog\git\tests>cd subm
让我们创建两个repos，每个repos有一个提交：
C:\Users\vonc\prog\git\tests\subm>git init s
Initialized empty Git repository in C:/Users/vonc/prog/git/tests/subm/s/.git/
C:\Users\vonc\prog\git\tests\subm>git init p
Initialized empty Git repository in C:/Users/vonc/prog/git/tests/subm/p/.git/
C:\Users\vonc\prog\git\tests\subm>cd s
C:\Users\vonc\prog\git\tests\subm\s>git commit --allow-empty -m "first s commit"
[master (root-commit) d11bd81] first s commit
C:\Users\vonc\prog\git\tests\subm\s>cd ..\p
C:\Users\vonc\prog\git\tests\subm\p>git commit --allow-empty -m "first p commit"
[master (root-commit) 10a7044] first p commit
我们将s添加为p（父级回购）的子模块
C:\Users\vonc\prog\git\tests\subm\p>git submodule add -- ../s
Cloning into 'C:/Users/vonc/prog/git/tests/subm/p/s'...
done.
C:\Users\vonc\prog\git\tests\subm\p>git st
On branch master
Changes to be committed:
(use "git reset HEAD <file>..." to unstage)
new file: .gitmodules
new file: s
C:\Users\vonc\prog\git\tests\subm\p>git commit -m "add p"
[master aa33ba9] add p
2 files changed, 4 insertions(+)
create mode 100644 .gitmodules
create mode 160000 s
现在让我们修改s repo，为其master分支添加新的提交
C:\Users\vonc\prog\git\tests\subm\p>cd ..\s
C:\Users\vonc\prog\git\tests\subm\s>git commit --allow-empty -m "second s commit"
[master 81e4800] second s commit
C:\Users\vonc\prog\git\tests\subm\s>gl
* 81e4800 - (HEAD -> master) second s commit (1 second ago) <VonC>
* d11bd81 - first s commit (3 minutes ago) <VonC>
让我们在父仓库中创建一个新的分支
C:\Users\vonc\prog\git\tests\subm\s>cd ..\p
C:\Users\vonc\prog\git\tests\subm\p>git commit --allow-empty -m "second s commit"
C:\Users\vonc\prog\git\tests\subm\p>git checkout -b branch
Switched to a new branch 'branch'
让我们更新子模块，并将其添加到新分支branch：
C:\Users\vonc\prog\git\tests\subm\p>git submodule update --remote
remote: Counting objects: 1, done.
remote: Total 1 (delta 0), reused 0 (delta 0)
Unpacking objects: 100% (1/1), done.
From C:/Users/vonc/prog/git/tests/subm/s
d11bd81..81e4800 master -> origin/master
Submodule path 's': checked out '81e48007afc90aceca16d884d0fdc34074121732'
C:\Users\vonc\prog\git\tests\subm\p>git st
On branch 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: s (new commits)
no changes added to commit (use "git add" and/or "git commit -a")
C:\Users\vonc\prog\git\tests\subm\p>git add .
C:\Users\vonc\prog\git\tests\subm\p>git commit -m "update s to latest master"
[branch 271a4fb] update s to latest master
1 file changed, 1 insertion(+), 1 deletion(-)
C:\Users\vonc\prog\git\tests\subm\p>cat .git\modules\s\HEAD
81e48007afc90aceca16d884d0fdc34074121732
C:\Users\vonc\prog\git\tests\subm\p>gl
* 271a4fb - (HEAD -> branch) update s to latest master (26 seconds ago) <VonC>
* f86aab2 - (master) second s commit (2 minutes ago) <VonC>
* aa33ba9 - add p (3 minutes ago) <VonC>
* 10a7044 - first p commit (4 minutes ago) <VonC>
我结帐master，检出了正确的子模块SHA1，但子模块的内容尚未更改。
C:\Users\vonc\prog\git\tests\subm\p>git checkout master
M s
Switched to branch 'master'
C:\Users\vonc\prog\git\tests\subm\p>cat .git\modules\s\HEAD
81e48007afc90aceca16d884d0fdc34074121732
C:\Users\vonc\prog\git\tests\subm\p>git st
On branch master
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: s (new commits)
no changes added to commit (use "git add" and/or "git commit -a")
如果我要切换回分支branch，状态将是干净的（这是因为子模块s的内容与其记录的gitlink SHA1匹配）
C:\Users\vonc\prog\git\tests\subm\p>git checkout branch
Switched to branch 'branch'
C:\Users\vonc\prog\git\tests\subm\p>git st
On branch branch
nothing to commit, working directory clean
但在master上，我需要submodule update将子模块s的内容重置为其SHA1：
C:\Users\vonc\prog\git\tests\subm\p>git checkout master
M s
Switched to branch 'master'
C:\Users\vonc\prog\git\tests\subm\p>git submodule update
Submodule path 's': checked out 'd11bd8132971a18e3e7cd19984cc6ce106478087'
C:\Users\vonc\prog\git\tests\subm\p>cat .git\modules\s\HEAD
d11bd8132971a18e3e7cd19984cc6ce106478087
C:\Users\vonc\prog\git\tests\subm\p>git st
On branch master
nothing to commit, working directory clean
结帐branch时会出现同样的问题：
C:\Users\vonc\prog\git\tests\subm\p>
C:\Users\vonc\prog\git\tests\subm\p>git checkout branch
M s
Switched to branch 'branch'
C:\Users\vonc\prog\git\tests\subm\p>git st
On branch 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: s (new commits)
no changes added to commit (use "git add" and/or "git commit -a")
C:\Users\vonc\prog\git\tests\subm\p>git show s
commit 271a4fb6bf79e2524f98dfbd505b2876b0c173a8
Author: VonC <vonc@laposte.net>
Date: Sat Jul 9 06:52:57 2016 +0200
update s to latest master
diff --git a/s b/s
index d11bd81..81e4800 160000
--- a/s
+++ b/s
@@ -1 +1 @@
-Subproject commit d11bd8132971a18e3e7cd19984cc6ce106478087
+Subproject commit 81e48007afc90aceca16d884d0fdc34074121732
同样，git submodule update会将子模块s的内容重置为父回购的分支branch中记录的SHA1。