How to resolve the Git error "refusing to merge unrelated histories"

When using Git, you may encounter the error message: refusing to merge unrelated histories. This error typically occurs when trying to merge two repositories that do not share a common history. This guide provides a detailed explanation of why this error occurs and how to resolve it effectively.

Understanding the error

The refusing to merge unrelated histories error happens when you attempt to merge branches or repositories that Git perceives as having no common commit history. This situation often arises in scenarios such as:

• Merging an initial commit of a new repository with an existing one.
• Combining two completely separate repositories.
• Pulling changes from a remote repository into a new local repository.

Steps to resolve the error

To resolve the refusing to merge unrelated histories error, you need to instruct Git to allow merging of unrelated histories. This can be done using the --allow-unrelated-histories flag.

Example scenario

Let’s consider a scenario where you want to merge changes from a remote repository into your local repository, but Git throws the error due to unrelated histories.

Step-by-step guide

1. Clone or initialize your repositories:

   If you haven't already, clone the remote repository and navigate to your local repository directory. Here are the commands for cloning and initializing:

   Terminal

   git clone <remote-repo-url> remote-repo
   cd remote-repo
   
   

   Or initialize a new local repository if you don't have one:

   Terminal

   mkdir local-repo
   cd local-repo
   git init
   
   

2. Add the remote repository:

   Add the remote repository to your local repository as a new remote:

   Terminal

   git remote add origin <remote-repo-url>
   
   

3. Fetch the changes from the remote repository:

   Fetch the changes from the remote repository:

   Terminal

   git fetch origin
   
   

4. Merge the remote branch with the --allow-unrelated-histories flag:

   Attempt to merge the remote branch (e.g., main) into your local branch (e.g., main) using the --allow-unrelated-histories flag:

   Terminal

   git merge origin/main --allow-unrelated-histories
   
   

   This command tells Git to permit the merge despite the lack of shared history between the branches.

5. Resolve any conflicts:

   If there are any merge conflicts, Git will prompt you to resolve them. Open the conflicted files, resolve the conflicts, and then mark the files as resolved:

   Terminal

   git add <file-with-conflict>
   
   

6. Commit the merge:

   After resolving conflicts, commit the merge:

   Terminal

   git commit
   
   

   Provide a commit message describing the merge and conflict resolution.

7. Push the changes to the remote repository:

   Finally, push the merged changes back to the remote repository:

   Terminal

   git push origin main
   
   

Additional scenarios

• Merging two completely separate repositories:

  If you are combining two distinct repositories, follow similar steps but ensure that you add both repositories as remotes and fetch changes from each. Use the --allow-unrelated-histories flag when merging their branches.

• Pulling changes into a new local repository:

  If you have a new local repository and want to pull changes from an existing remote repository, use the --allow-unrelated-histories flag during the pull operation:

  Terminal

  git pull origin main --allow-unrelated-histories
  
  

If after following these steps and you are still seeing the Git error refusing to merge unrelated histories, see the official Git documentation for more details.