Recently, I worked on merging two separate projects into one. Each project had its own Git repository, and I wanted to combine them into a single repository while preserving the commit history.
Initially, I copied the code from one project, pasted it into the other, and committed the changes. If anyone needed information on the original commits, they could look at the original repo. However, it was suggested to me that it was possible to copy over the history of the commits from the original repository.
Let’s look at how we can do this.
I will refer to the two repositories as project1 and project2, each with its own Git repository located at project1Url and project2Url, respectively.
Step 1: Clone the original repository
First, clone the repository of project1:
git clone project1Url
Step 2: Add the new repository as a remote
Next, add the repository of project2 as a remote:
git remote add project2 project2Url
Step 3: Fetch the commits from the new repository
Fetch the commits from the project2 repository:
git fetch project2
Step 4: Merge the commits from the new repository
Merge the commits from the project2 repository into project1:
git merge project2/develop --allow-unrelated-histories
Step 5: Fix merge conflicts
If there are conflicts, you will need to resolve them. In my case, this was mainly build files and scripts in the root of the repository. Most of the important code was in subfolders, so this was minimal.
Step 6: Push the changes to the original repository
Push the changes to a new branch for review before merging into the main branch:
git checkout -b feature/merge-project2-into-project1
git push origin feature/merge-project2-into-project1
Step 7: Clean up
Test your code to ensure everything builds and runs as expected now that it is all in one repository. Create a Pull Request and review all the changes to ensure nothing gets changed that shouldn’t be.
When you look at your PR, it will look like a lot of code has been added. However, if you look closely at the Git history of those files, you will see that the history has been preserved from the original repository.
Conclusion
This is a remarkably simple way to preserve the history of commits from one repository to another. It is a great way to merge two projects into one repository and keep the history of the commits. A similar process could be followed if you want to create a new repository and merge other repositories into it.
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