content/get-started/using-git/about-git-subtree-merges.md

---
title: About Git subtree merges
redirect_from:
  - /articles/working-with-subtree-merge
  - /subtree-merge
  - /articles/about-git-subtree-merges
  - /github/using-git/about-git-subtree-merges
  - /github/getting-started-with-github/about-git-subtree-merges
  - /github/getting-started-with-github/using-git/about-git-subtree-merges
intro: 'If you need to manage multiple projects within a single repository, you can use a *subtree merge* to handle all the references.'
versions:
  fpt: '*'
  ghes: '*'
  ghec: '*'
---
## About subtree merges

Typically, a subtree merge is used to contain a repository within a repository. The "subrepository" is stored in a folder of the main repository.

The best way to explain subtree merges is to show by example. We will:

* Make an empty repository called `test` that represents our project.
* Merge another repository into it as a subtree called `Spoon-Knife`.
* The `test` project will use that subproject as if it were part of the same repository.
* Fetch updates from `Spoon-Knife` into our `test` project.

## Setting up the empty repository for a subtree merge

{% data reusables.command_line.open_the_multi_os_terminal %}
1. Create a new directory and navigate to it.

   ```shell
   mkdir test
   cd test
   ```

1. Initialize a new Git repository.

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

1. Create and commit a new file.

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

## Adding a new repository as a subtree

1. Add a new remote URL pointing to the separate project that we're interested in.

   ```shell
   $ git remote add -f spoon-knife https://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 https://github.com/octocat/Spoon-Knife
   >  * [new branch]      main     -> Spoon-Knife/main
   ```

1. Merge the `Spoon-Knife` project into the local Git project. This doesn't change any of your files locally, but it does prepare Git for the next step.

   If you're using Git 2.9 or above:

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

   If you're using Git 2.8 or below:

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

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

   ```shell
   $ git read-tree --prefix=spoon-knife/ -u spoon-knife/main
   > fatal: refusing to merge unrelated histories
   ```

1. Commit the changes to keep them safe.

   ```shell
   $ git commit -m "Subtree merged in spoon-knife"
   > [main fe0ca25] Subtree merged in spoon-knife
   ```

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

> [!TIP]
> If you create a fresh clone of the repository in the future, the remotes you've added will not be created for you. You will have to add them again using [the `git remote add` command](/get-started/git-basics/managing-remote-repositories).

## 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:

```shell
git pull -s subtree REMOTE-NAME BRANCH-NAME
```

For the example above, this would be:

```shell
git pull -s subtree spoon-knife main
```

## Further reading

* [The "Advanced Merging" chapter from the _Pro Git_ book](https://git-scm.com/book/en/v2/Git-Tools-Advanced-Merging)
* [How to use the subtree merge strategy](https://www.kernel.org/pub/software/scm/git/docs/howto/using-merge-subtree.html)