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27 Mar 2012 Comments

Git Submodule使用完整教程

自从看了蒋鑫的《Git权威指南》之后就开始使用Git Submodule功能,团队也都熟悉了怎么使用,多个子系统(模块)都能及时更新到最新的公共资源,把使用的过程以及经验和容易遇到的问题分享给大家。

Git Submodule功能刚刚开始学习可能觉得有点怪异,所以本教程把每一步的操作的命令和结果都用代码的形式展现给大家,以便更好的理解。

1.对于公共资源各种程序员的处理方式

每个公司的系统都会有一套统一的系统风格,或者针对某一个大客户的多个系统风格保持统一,而且如果风格改动后要同步到多个系统中;这样的需求几乎每个开发人员都遇到,下面看看各个层次的程序员怎么处理:

假如对于系统的风格需要几个目录:css、images、js。

  • 普通程序员,把最新版本的代码逐个复制到每个项目中,如果有N个项目,那就是要复制N x 3次;如果漏掉了某个文件夹没有复制…@(&#@#。

  • 文艺程序员,使用Git Submodule功能,执行:git submodule update,然后冲一杯咖啡悠哉的享受着。


引用一段《Git权威指南》的话: 项目的版本库在某些情况虾需要引用其他版本库中的文件,例如公司积累了一套常用的函数库,被多个项目调用,显然这个函数库的代码不能直接放到某个项目的代码中,而是要独立为一个代码库,那么其他项目要调用公共函数库该如何处理呢?分别把公共函数库的文件拷贝到各自的项目中会造成冗余,丢弃了公共函数库的维护历史,这显然不是好的方法。

2.开始学习Git Submodule

“工欲善其事,必先利其器”!

既然文艺程序员那么轻松就搞定了,那我们就把过程一一道来。

说明:本例采用两个项目以及两个公共类库演示对submodule的操作。因为在一写资料或者书上的例子都是一个项目对应1~N个lib,但是实际应用往往并不是这么简单。

2.1 创建Git Submodule测试项目

2.1.1 准备环境

➜ henryyan@hy-hp  ~  pwd
/home/henryyan
mkdir -p submd/repos

创建需要的本地仓库:

cd ~/submd/repos
git --git-dir=lib1.git init --bare
git --git-dir=lib2.git init --bare
git --git-dir=project1.git init --bare
git --git-dir=project2.git init --bare

初始化工作区:

mkdir ~/submd/ws
cd ~/submd/ws

2.1.2 初始化项目

初始化project1:

➜ henryyan@hy-hp  ~/submd/ws  git clone ../repos/project1.git 
Cloning into project1...
done.
warning: You appear to have cloned an empty repository.

➜ henryyan@hy-hp  ~/submd/ws  cd project1
➜ henryyan@hy-hp  ~/submd/ws/project1 git:(master) echo "project1" > project-infos.txt
➜ henryyan@hy-hp  ~/submd/ws/project1 git:(master) ✗ ls
project-infos.txt

➜ henryyan@hy-hp  ~/submd/ws/project1 git:(master) ✗ git add project-infos.txt 
➜ henryyan@hy-hp  ~/submd/ws/project1 git:(master) ✗ git status
# On branch master
#
# Initial commit
#
# Changes to be committed:
#   (use "git rm --cached ..." to unstage)
#
#   new file:   project-infos.txt
#
➜ henryyan@hy-hp  ~/submd/ws/project1 git:(master) ✗ git commit -m "init project1"
[master (root-commit) 473a2e2] init project1
 1 files changed, 1 insertions(+), 0 deletions(-)
 create mode 100644 project-infos.txt
➜ henryyan@hy-hp  ~/submd/ws/project1 git:(master) git push origin master
Counting objects: 3, done.
Writing objects: 100% (3/3), 232 bytes, done.
Total 3 (delta 0), reused 0 (delta 0)
Unpacking objects: 100% (3/3), done.
To /home/henryyan/submd/ws/../repos/project1.git
 * [new branch]      master -> master

初始化project2:


➜ henryyan@hy-hp  ~/submd/ws/project1 cd ..
➜ henryyan@hy-hp  ~/submd/ws  git clone ../repos/project2.git 
Cloning into project2...
done.
warning: You appear to have cloned an empty repository.

➜ henryyan@hy-hp  ~/submd/ws  cd project2
➜ henryyan@hy-hp  ~/submd/ws/project2 git:(master) echo "project2" > project-infos.txt
➜ henryyan@hy-hp  ~/submd/ws/project2 git:(master) ✗ ls
project-infos.txt

➜ henryyan@hy-hp  ~/submd/ws/project2 git:(master) ✗ git add project-infos.txt 
➜ henryyan@hy-hp  ~/submd/ws/project2 git:(master) ✗ git status
# On branch master
#
# Initial commit
#
# Changes to be committed:
#   (use "git rm --cached ..." to unstage)
#
#   new file:   project-infos.txt
#
➜ henryyan@hy-hp  ~/submd/ws/project2 git:(master) ✗ git commit -m "init project2"
[master (root-commit) 473a2e2] init project2
 1 files changed, 1 insertions(+), 0 deletions(-)
 create mode 100644 project-infos.txt
➜ henryyan@hy-hp  ~/submd/ws/project2 git:(master) git push origin master
Counting objects: 3, done.
Writing objects: 100% (3/3), 232 bytes, done.
Total 3 (delta 0), reused 0 (delta 0)
Unpacking objects: 100% (3/3), done.
To /home/henryyan/submd/ws/../repos/project2.git
 * [new branch]      master -> master

2.1.3 初始化公共类库

初始化公共类库lib1:

➜ henryyan@hy-hp  ~/submd/ws  git clone ../repos/lib1.git 
Cloning into lib1...
done.
warning: You appear to have cloned an empty repository.
➜ henryyan@hy-hp  ~/submd/ws  cd lib1 
➜ henryyan@hy-hp  ~/submd/ws/lib1 git:(master) echo "I'm lib1." > lib1-features
➜ henryyan@hy-hp  ~/submd/ws/lib1 git:(master) ✗ git add lib1-features 
➜ henryyan@hy-hp  ~/submd/ws/lib1 git:(master) ✗ git commit -m "init lib1"
[master (root-commit) c22aff8] init lib1
 1 files changed, 1 insertions(+), 0 deletions(-)
 create mode 100644 lib1-features
➜ henryyan@hy-hp  ~/submd/ws/lib1 git:(master) git push origin master
Counting objects: 3, done.
Writing objects: 100% (3/3), 227 bytes, done.
Total 3 (delta 0), reused 0 (delta 0)
Unpacking objects: 100% (3/3), done.
To /home/henryyan/submd/ws/../repos/lib1.git
 * [new branch]      master -> master

初始化公共类库lib2:

➜ henryyan@hy-hp  ~/submd/ws/lib1 git:(master) cd ..
➜ henryyan@hy-hp  ~/submd/ws  git clone ../repos/lib2.git 
Cloning into lib2...
done.
warning: You appear to have cloned an empty repository.
➜ henryyan@hy-hp  ~/submd/ws  cd lib2 
➜ henryyan@hy-hp  ~/submd/ws/lib2 git:(master) echo "I'm lib2." > lib2-features
➜ henryyan@hy-hp  ~/submd/ws/lib2 git:(master) ✗ git add lib2-features 
➜ henryyan@hy-hp  ~/submd/ws/lib2 git:(master) ✗ git commit -m "init lib2"
[master (root-commit) c22aff8] init lib2
 1 files changed, 1 insertions(+), 0 deletions(-)
 create mode 100644 lib2-features
➜ henryyan@hy-hp  ~/submd/ws/lib2 git:(master) git push origin master
Counting objects: 3, done.
Writing objects: 100% (3/3), 227 bytes, done.
Total 3 (delta 0), reused 0 (delta 0)
Unpacking objects: 100% (3/3), done.
To /home/henryyan/submd/ws/../repos/lib2.git
 * [new branch]      master -> master

2.2 为主项目添加Submodules

2.2.1 为project1添加lib1和lib2

➜ henryyan@hy-hp  ~/submd/ws/lib2 git:(master) cd ../project1 
➜ henryyan@hy-hp  ~/submd/ws/project1 git:(master) ls
project-infos.txt
➜ henryyan@hy-hp  ~/submd/ws/project1 git:(master) git submodule add ~/submd/repos/lib1.git libs/lib1
Cloning into libs/lib1...
done.
➜ henryyan@hy-hp  ~/submd/ws/project1 git:(master) ✗ git submodule add ~/submd/repos/lib2.git libs/lib2
Cloning into libs/lib2...
done.
➜ henryyan@hy-hp  ~/submd/ws/project1 git:(master) ✗ ls
libs  project-infos.txt
➜ henryyan@hy-hp  ~/submd/ws/project1 git:(master) ✗ ls libs 
lib1  lib2

➜ henryyan@hy-hp  ~/submd/ws/project1 git:(master) ✗ git status 
# On branch master
# Changes to be committed:
#   (use "git reset HEAD ..." to unstage)
#
#   new file:   .gitmodules
#   new file:   libs/lib1
#   new file:   libs/lib2
#

# 查看一下公共类库的内容

➜ henryyan@hy-hp  ~/submd/ws/project1 git:(master) cat libs/lib1/lib1-features 
I'm lib1.
➜ henryyan@hy-hp  ~/submd/ws/project1 git:(master) cat libs/lib2/lib2-features
I'm lib2.

好了,到目前为止我们已经使用git submodule add命令为project1成功添加了两个公共类库(lib1、lib2),查看了当前的状态发现添加了一个新文件(.gitmodules)和两个文件夹(libs/lib1、libs/lib2);那么新增的.gitmodules文件是做什么用的呢?我们查看一下文件内容便知晓了:

n@hy-hp  ~/submd/ws/project1 git:(master) ✗ cat .gitmodules 
[submodule "libs/lib1"]
    path = libs/lib1
    url = /home/henryyan/submd/repos/lib1.git
[submodule "libs/lib2"]
    path = libs/lib2
    url = /home/henryyan/submd/repos/lib2.git

原来如此,.gitmodules记录了每个submodule的引用信息,知道在当前项目的位置以及仓库的所在。

好的,我们现在把更改提交到仓库。

➜ henryyan@hy-hp  ~/submd/ws/project1 git:(master) ✗ git commit -a -m "add submodules[lib1,lib2] to project1"
[master 7157977] add submodules[lib1,lib2] to project1
 3 files changed, 8 insertions(+), 0 deletions(-)
 create mode 100644 .gitmodules
 create mode 160000 libs/lib1
 create mode 160000 libs/lib2

➜ henryyan@hy-hp  ~/submd/ws/project1 git:(master) git push
Counting objects: 5, done.
Delta compression using up to 2 threads.
Compressing objects: 100% (4/4), done.
Writing objects: 100% (4/4), 491 bytes, done.
Total 4 (delta 0), reused 0 (delta 0)
Unpacking objects: 100% (4/4), done.
To /home/henryyan/submd/ws/../repos/project1.git
   45cbbcb..7157977  master -> master
假如你是第一次引入公共类库的开发人员,那么项目组的其他成员怎么Clone带有Submodule的项目呢,下面我们再clone一个项目讲解如何操作。

2.3 Clone带有Submodule的仓库

模拟开发人员B……

➜ henryyan@hy-hp  ~/submd/ws/project1 git:(master) cd ~/submd/ws
➜ henryyan@hy-hp  ~/submd/ws  git clone ../repos/project1.git project1-b
Cloning into project1-b...
done.
➜ henryyan@hy-hp  ~/submd/ws  cd project1-b 
➜ henryyan@hy-hp  ~/submd/ws/project1-b git:(master) git submodule 
-c22aff85be91eca442734dcb07115ffe526b13a1 libs/lib1
-7290dce0062bd77df1d83b27dd3fa3f25a836b54 libs/lib2

看到submodules的状态是hash码和文件目录,但是注意前面有一个减号:-,含义是该子模块还没有检出。

OK,检出project1-b的submodules……

➜ henryyan@hy-hp  ~/submd/ws/project1-b git:(master) git submodule init
Submodule 'libs/lib1' (/home/henryyan/submd/repos/lib1.git) registered for path 'libs/lib1'
Submodule 'libs/lib2' (/home/henryyan/submd/repos/lib2.git) registered for path 'libs/lib2'
➜ henryyan@hy-hp  ~/submd/ws/project1-b git:(master) git submodule update
Cloning into libs/lib1...
done.
Submodule path 'libs/lib1': checked out 'c22aff85be91eca442734dcb07115ffe526b13a1'
Cloning into libs/lib2...
done.
Submodule path 'libs/lib2': checked out '7290dce0062bd77df1d83b27dd3fa3f25a836b54'
读者可以查看:.git/config文件的内容,最下面有submodule的注册信息!

验证一下类库的文件是否存在:

➜ henryyan@hy-hp  ~/submd/ws/project1-b git:(master) cat libs/lib1/lib1-features libs/lib2/lib2-features 
I'm lib1.
I'm lib2.
上面的两个命令(git submodule init & update)其实可以简化,后面会讲到!

2.3 修改Submodule

我们在开发人员B的项目上修改Submodule的内容。

先看一下当前Submodule的状态:

➜ henryyan@hy-hp  ~/submd/ws/project1-b git:(master) cd libs/lib1
➜ henryyan@hy-hp  ~/submd/ws/project1-b/libs/lib1  git status
# Not currently on any branch.
nothing to commit (working directory clean)

为什么是Not currently on any branch呢?不是应该默认在master分支吗?别急,一一解答!

Git对于Sub