如何将git子模块恢复到其提交的版本？

Question

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，那么子模块引用似乎已经被修改了。

例如（哈希值可能不同，并且您可能必须向下滚动代码窗口才能查看所有行）：

# 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

当检出主分支后，子模块的哈希值会发生变化，就好像在其他分支中进行的更新也影响了主分支。

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

这会显示添加到主分支中的子模块提交。

如何在工作树中在分支之间切换，并使子模块的提交与其提交时相匹配？或者当更改分支时，子模块显示为已修改但在该分支中未进行修改时，如何恢复？

- wdkendall

Answer 1

我刚刚使用git 2.9.0复现了这个问题

你只需要在最后执行以下操作即可得到一个干净的主分支：

git submodule update

那将重置子模块为其master值，并且.git/modules/example-sub/HEAD将具有正确的值。

当您再次检出otherbranch时，您将遇到相同的问题。正确的gitlink（索引中的特殊条目）将被检出。但是.git/modules/example-sub/HEAD不会立即更改。

在这两种情况下，这是因为checkout只修改了gitlink，而没有修改子模块的内容。只有git submodule update才会实际将子模块的内容检出到其记录的gitlink SHA1。

这样，如果您在子模块中进行了正在进行的工作，则不会被父存储库中的checkout擦除。

---

这是我的独立实验：

C:\Users\vonc\prog\git\tests>mkdir subm
C:\Users\vonc\prog\git\tests>cd subm

让我们创建两个仓库，每个仓库都有一个提交：

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

让我们将s作为p（父仓库）的子模块添加

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 仓库，在其 master 分支上添加一个新的提交。

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>

让我们在父代码库中创建一个新分支

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中：

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>

如果我检出了master，正确的子模块SHA1将被检出，但是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")

如果我切换回分支branch，状态将会是干净的（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

但是在主分支上，我需要执行submodule update命令来将子模块s的内容重置为其SHA1值:

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

当我检出branch时，会出现相同的问题：

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 <[e-mail]>
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

再次运行 git submodule update 命令将会将子模块 s 的内容重置为父仓库分支 branch 中记录的 SHA1。

- VonC

---

感谢您的回答和提供的链接。 - wdkendall