subtrees in Git: How to split Directories into individual standalone repositories

02-04-2021 382 words 2 minutes

Contents

Problem

You start working on an idea without having to bother if the project needs to split into smaller components, projects. Once the vision starts becomes clear and the horizon becomes clear, it makes sense to start thinking into managing components as their own standalone software repositories.

One does not want to put a lot of effort towards this migration, and not mess the History your git repository has. Credit from your colleagues should be manifested fairly in the new repositories.

How does one achieve this?

Current Structure

$ cd big-repository
# MEGA-REPOSITORY
.
├── SubProject1 # this should be a standalone repository
│   └── SubModule1
└── SubProject2 # this should be a standalone repository
    ├── SubModule1
    ├── SubModule2
    └── tests

Solution

The great thing about git is it diversified eco-system. The problem of making directories their own git repositories is something a large pool of IT Developers face. The solution is to make the subprojects into a subtree.

Usage

$ git subtree split --prefix <your_directory_name> --branch <branch_name>

here branch_name can be whatever you wish it to be, your_directory_name here in my case is SubProject1 and SubProject2.

$ git subtree split --prefix SubProject1 --branch micro-project

git will make a branch called micro-project and check it out for you. Upon listing the files and directories it will only show the content of the directory mentioned (here, contents of SubProject1)

Similarly for SubProject2

$ git subtree split --prefix SubProject2 --branch nano-project

Setting Up Repositories

Initialize your Repositories on your Git Server / Platform (GitHub, GitLab etc.)

Create a new directory

 $ mkdir micro-project/ && cd micro-project/

Initialize the directory as a git repository
```
 $ git init
```
Pull the subtree branch in the big-repository to the current directory
```
 $ git pull ../path/to/big-repository <branch-name>
```
In our case for micro-project the branch name is micro-project
```
 $ git pull ../path/to/big-repository micro-project
```
You can verify if all the commit logs are still intact in the new repository using:
```
 $ git log --oneline
```

Add a remote to your new Repository using:

 $ git remote add origin <YOUR_GIT_SERVER_URL/micro-project.git>

Push to code to the Server:
```
 $ git push -u origin master
```

Continue the steps for nano-project too.