关于 Git 子树合并

通常，子树合并用于在仓库中包含仓库。 “子仓库”存储在主仓库的文件夹中。

解释子树合并的最佳方式是举例说明。 我们将：

• 创建一个名为 test 的空仓库，表示我们的项目
• 将另一个仓库 Spoon-Knife 作为子树合并到其中。
• 如果该子项目属于同一仓库，test 项目会使用它。
• 从 Spoon-Knife 提取更新到 test 项目。

创建用于子树合并的空仓库

1. Open TerminalTerminalGit Bashthe terminal.

2. 创建一个新目录并找到它。

   $ mkdir test
   $ cd test

3. 初始化新的 Git 仓库。

   $ git init
   > Initialized empty Git repository in /Users/octocat/tmp/test/.git/

4. 创建并提交新文件。

   $ touch .gitignore
   $ git add .gitignore
   $ git commit -m "initial commit"
   > [master (root-commit) 3146c2a] initial commit
   >  0 files changed, 0 insertions(+), 0 deletions(-)
   >  create mode 100644 .gitignore

Adding a new repository as a subtree

1. 新增指向我们感兴趣的单独项目的远程 URL。

   $ git remote add -f spoon-knife git@github.com:octocat/Spoon-Knife.git
   > Updating spoon-knife
   > warning: no common commits
   > remote: Counting objects: 1732, done.
   > remote: Compressing objects: 100% (750/750), done.
   > remote: Total 1732 (delta 1086), reused 1558 (delta 967)
   > Receiving objects: 100% (1732/1732), 528.19 KiB | 621 KiB/s, done.
   > Resolving deltas: 100% (1086/1086), done.
   > From git://github.com/octocat/Spoon-Knife
   >  * [new branch]      master     -> Spoon-Knife/master

2. Merge the Spoon-Knife project into the local Git project. 这不会在本地更改任何文件，但会为下一步准备 Git。

   If you're using Git 2.9 or above:

   $ git merge -s ours --no-commit --allow-unrelated-histories spoon-knife/master
   > Automatic merge went well; stopped before committing as requested

   If you're using Git 2.8 or below:

   $ git merge -s ours --no-commit spoon-knife/master
   > Automatic merge went well; stopped before committing as requested

3. Create a new directory called spoon-knife, and copy the Git history of the Spoon-Knife project into it.

   $ git read-tree --prefix=spoon-knife/ -u spoon-knife/master

4. 提交更改以确保其安全。

   $ git commit -m "Subtree merged in spoon-knife"
   > [master fe0ca25] Subtree merged in spoon-knife

Although we've only added one subproject, any number of subprojects can be incorporated into a Git repository.

Synchronizing with updates and changes

When a subproject is added, it is not automatically kept in sync with the upstream changes. You will need to update the subproject with the following command:

$ git pull -s subtree remotename branchname

对于上述示例，将是：

$ git pull -s subtree spoon-knife master

延伸阅读

• Pro Git 书籍中的“子树合并”一章
• "如何使用子树合并策略"