Git Submodule 使用简介

D瓜哥从去年开始,将所有的笔记都整合到了自建的 Wiki 中。整理分析,确实方便很多。

最近有两个部分,比较独立,自成系统。其中,有一个模块还考虑和其他小伙伴合作来搞。所以,就将这两部分抽取出来,独立成单独的项目来维护。但是,为方便查看和随时随地同步更新,正好可以使用 Git Submodule 特性。

另外,还有一种场景:开发的项目使用了第三方或者公司的基础库,使用同一个版本库肯定不合适,也不现实,这时就必须使用子模块来搞。

对 Git 不了解的,可以参考D瓜哥以前的文章:  Git&Github社区化协作使用指南 。下面,D瓜哥带领大家来学习一下  git submodule 的简单实用方法。 

添加子模块

从新建一个项目,或者从远处服务器上克隆一个项目,作为“顶级项目”。这里,D瓜哥就从 Github 上新建一个项目,然后再克隆下来: 

/Users/diguage  git clone git@github.com:diguage/parent.git

Cloning into 'parent'...
remote: Counting objects: 5, done.
remote: Compressing objects: 100% (5/5), done.
remote: Total 5 (delta 0), reused 0 (delta 0), pack-reused 0
Receiving objects: 100% (5/5), 4.59 KiB | 0 bytes/s, done.
Checking connectivity... done.

进入刚克隆下来的项目,我们来添加子模块。这里的子模块就必须从远处服务器上克隆了。另外,子模块可以放在项目的任意目录下,并且可以根据自己的需要重命名。D瓜哥这里这是为了方便演示,所以就直接放在子目录了。进入顶级项目,我们先看一下版本库的状态:

➜  /Users/diguage cd parent

➜  /Users/diguage/parent git:(master) git status

On branch master
Your branch is up-to-date with 'origin/master'.
nothing to commit, working directory clean

这里提示,项目中没有任何需要提交的东西。下面,我们开始添加子模块:

/Users/diguage/parent git:(master) git submodule add [email protected]:diguage/child.git

Cloning into 'child'...
remote: Counting objects: 5, done.
remote: Compressing objects: 100% (5/5), done.
remote: Total 5 (delta 0), reused 0 (delta 0), pack-reused 0
Receiving objects: 100% (5/5), 4.63 KiB | 0 bytes/s, done.
Checking connectivity... done.

这时,再看一下版本库的状态:

➜  /Users/diguage/parent git:(master) ✗ git status
On branch master
Your branch is up-to-date with 'origin/master'.
Changes to be committed:
  (use "git reset HEAD ..." to unstage)

	new file:   .gitmodules
	new file:   child

这时,我们看到,除了刚刚添加的  child 模块外,还多了一个  .gitmodules 文件。这个文件就是用于记录子模块的路径已经远程版本库地址的地方。这两个文件处于待提交的状态。下面把这个修改提交一下。 

➜  /Users/diguage/parent git:(master) ✗ git commit -am "增加子模块"

[master a05bfe0] 增加子模块
 2 files changed, 4 insertions(+)
 create mode 100644 .gitmodules
 create mode 160000 child


➜  /Users/diguage/parent git:(master) git push origin master

Counting objects: 3, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (3/3), done.
Writing objects: 100% (3/3), 452 bytes | 0 bytes/s, done.
Total 3 (delta 0), reused 0 (delta 0)
To [email protected]:diguage/parent.git
   e56cd5a..a05bfe0  master -> master

这时,大家可以登录到 Github 或者其他的版本库服务器上看一下项目的状态。D瓜哥就不贴图了。

至此,添加子模块的工作已经完成。下面,我们来看一看如何更新。

更新子模块

当我们添加完子模块后,过段时间后,子模块有更新,这时候,我们就需要更新了。我们来看一下如何更新。

方式一

这个方式略微显得有的“笨拙”,但是大智若愚,大巧若拙,万变不离其宗。最笨的招数也许也是最实用的招数。扯了这么多,其实很简单,就是进入到每一个子模块,执行  git pull origin master 。 

/Users/diguage/parent git:(master) cd child

➜  /Users/diguage/parent/child git:(master) git pull origin master

remote: Counting objects: 3, done.
remote: Compressing objects: 100% (3/3), done.
remote: Total 3 (delta 2), reused 0 (delta 0), pack-reused 0
Unpacking objects: 100% (3/3), done.
From github.com:diguage/child
 * branch            master     -> FETCH_HEAD
   d4ec39a..1b855a4  master     -> origin/master
Updating d4ec39a..1b855a4
Fast-forward
 README.md | 3 +++
 1 file changed, 3 insertions(+)

这时,我们再进入到顶级项目中,查看一下项目状态:

➜  /Users/diguage/parent/child git:(master) cd ..

➜  /Users/diguage/parent git:(master) ✗ git status

On branch master
Your branch is up-to-date with 'origin/master'.
Changes not staged for commit:
  (use "git add ..." to update what will be committed)
  (use "git checkout -- ..." to discard changes in working directory)

	modified:   child (new commits)

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

这里可以看到明显的提示,在项目有一个新的提交。为什么会这样呢?其实,Git 在顶级项目中记录了一个子模块的提交日志的指针,用于保存子模块的提交日志所处的位置,以保证无论子模块是否有新的提交,在任何一个地方克隆下顶级项目时,各个子模块的记录是一致的。避免因为所引用的子模块不一致导致的潜在问题。如果我们更新了子模块,我们需要把这个最近的记录提交到版本库中,以方便和其他人协同。这也是刚刚添加完子模块后还要在顶级项目中提交一次的原因。

➜  /Users/diguage/parent git:(master) ✗ git commit -am "更新子模块"

[master 5ac4dbb] 更新子模块
 1 file changed, 1 insertion(+), 1 deletion(-)


➜  /Users/diguage/parent git:(master) git push origin master

Counting objects: 2, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (2/2), done.
Writing objects: 100% (2/2), 259 bytes | 0 bytes/s, done.
Total 2 (delta 1), reused 0 (delta 0)
To [email protected]:diguage/parent.git
   a05bfe0..5ac4dbb  master -> master

这里D瓜哥再多说一句:进入子模块目录后,你就当做这是一个独立的项目,可以正常进行一个普通 Git 项目所执行的任何操作。更新完正常的修改、添加任务后,把所做的修改提交,然后推送到远处版本库上。然后,如果需要记得在顶级项目中,也做一次提交,修改一下顶级项目所引用的子模块的提交日志的“指针”。

克隆项目

当多人合作搞一个项目,或者需要同步公司电脑的代码到家里电脑上,就需要从远处版本库上克隆项目代码。这时,可以使用两种方式。

方式一

古语有云:由俭入奢易,由奢入俭难。所以,D瓜哥决定先从比较麻烦的方式入手。下面开始:

➜  /Users/diguage  git clone git@github.com:diguage/parent.git  # 第一步

Cloning into 'parent'...
remote: Counting objects: 10, done.
remote: Compressing objects: 100% (9/9), done.
remote: Total 10 (delta 2), reused 5 (delta 1), pack-reused 0
Receiving objects: 100% (10/10), 5.11 KiB | 0 bytes/s, done.
Resolving deltas: 100% (2/2), done.
Checking connectivity... done.


➜  /Users/diguage  cd parent


➜  /Users/diguage/parent git:(master) git submodule update --init --recursive  # 第二步

Submodule 'child' (git@github.com:diguage/child.git) registered for path 'child'
Cloning into 'child'...
remote: Counting objects: 8, done.
remote: Compressing objects: 100% (8/8), done.
remote: Total 8 (delta 2), reused 0 (delta 0), pack-reused 0
Receiving objects: 100% (8/8), 4.91 KiB | 0 bytes/s, done.
Resolving deltas: 100% (2/2), done.
Checking connectivity... done.
Submodule path 'child': checked out '1b855a4987b44e7530dbd9904dee089fb31f3525'


➜  /Users/diguage/parent git:(master) cd child


➜  /Users/diguage/parent/child git:((1b855a4...)) git status # 第三步

HEAD detached at 1b855a4
nothing to commit, working directory clean


➜  /Users/diguage/parent/child git:((1b855a4...)) git checkout master # 第四步

Switched to branch 'master'
Your branch is up-to-date with 'origin/master'.

这里需要大概四步,确实挺复杂。下面我们来看一看稍微简单一点的。

方式二

➜  /Users/diguage  git clone --recursive git@github.com:diguage/parent.git  # 第一步

Cloning into 'parent'...
remote: Counting objects: 10, done.
remote: Compressing objects: 100% (9/9), done.
remote: Total 10 (delta 2), reused 5 (delta 1), pack-reused 0
Receiving objects: 100% (10/10), 5.11 KiB | 0 bytes/s, done.
Resolving deltas: 100% (2/2), done.
Checking connectivity... done.
Submodule 'child' (git@github.com:diguage/child.git) registered for path 'child'
Cloning into 'child'...
remote: Counting objects: 8, done.
remote: Compressing objects: 100% (8/8), done.
remote: Total 8 (delta 2), reused 0 (delta 0), pack-reused 0
Receiving objects: 100% (8/8), 4.91 KiB | 0 bytes/s, done.
Resolving deltas: 100% (2/2), done.
Checking connectivity... done.
Submodule path 'child': checked out '1b855a4987b44e7530dbd9904dee089fb31f3525'


➜  /Users/diguage  cd parent/child


➜  /Users/diguage/parent/child git:((1b855a4...)) git status # 第二步

HEAD detached at 1b855a4
nothing to commit, working directory clean


➜  /Users/diguage/parent/child git:((1b855a4...)) git checkout master # 第三步

Switched to branch 'master'
Your branch is up-to-date with 'origin/master'.

这种方式确实比上面简单多了,少了一条命令。(别笑!严肃点,哥是认真的!)

删除子模块

也许未来有一天,我们项目成功了,公司上市了,可以不再引用别人的代码,自己早轮子了,那么我们就可以把子模块从版本库中删除。D瓜哥原以为很麻烦,今天为了写文章,特意试了一下,其实很简单。(我艹,哥是不是暴露了什么?!)如下:

➜  /Users/diguage/parent git:(master) git rm child

rm 'child'


➜  /Users/diguage/parent git:(master) ✗ git status

On branch master
Your branch is up-to-date with 'origin/master'.
Changes to be committed:
  (use "git reset HEAD ..." to unstage)

	modified:   .gitmodules
	deleted:    child


➜  /Users/diguage/parent git:(master) ✗ git commit -am "删除子模块"

[master b0b088b] 删除子模块
 2 files changed, 4 deletions(-)
 delete mode 160000 child


➜  /Users/diguage/parent git:(master) git push origin master

Counting objects: 3, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (2/2), done.
Writing objects: 100% (3/3), 274 bytes | 0 bytes/s, done.
Total 3 (delta 1), reused 0 (delta 0)
To [email protected]:diguage/parent.git
   5ac4dbb..b0b088b  master -> master

直接一条命令就搞定了:  git rm  。 

参考资料

  • Pro Git – 子模块
  • Git 进阶:Submodule
  • Git 进阶指南
原文地址:http://www.tuicool.com/articles/jqiEJzU

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