Merge error refusing to merge unrelated histories

What is the ‘fatal: refusing to merge unrelated histories’ error?

The fatal: refusing to merge histories error is a fairly common Git error. It appears when a developer tries to merge two unrelated projects into a single branch.

This error appears when the branch has its commit histories and tags incompatible with the pull request or clone.

Why does ‘fatal: refusing to merge unrelated histories’ happen?

How to resolve ‘fatal: refusing to merge unrelated histories’

There are two ways of solving the fatal: refusing to merge unrelated histories error.

Option 1: Use ‘–allow-unrelated-histories’

One way to solve the issue is to use the --allow-unrelated-histories git flag.

Here the git command will look something like this: git pull origin master --allow-unrelated-histories.

You can substitute origin with the remote repository you are pulling from. You can also replace the master branch with whatever branch you want the pull request to merge into.

The idea behind --allow-unrelated-histories is that git lets you merge unrelated branches. This git flag works seamlessly when there are no file conflicts.

However, in reality, at least one thing pops up, and you will need to use the normal Git resolution flow to resolve them.

Here is an example of what a common conflict may look like when trying to merge branches:

 Auto-merging package.json
 CONFLICT (add/add): Merge conflict in package.json
 Auto-merging package-lock.json
 CONFLICT (add/add): Merge conflict in package-lock.json
 Auto-merging README.md
 CONFLICT (add/add): Merge conflict in README.md
 Auto-merging .gitignore
 CONFLICT (add/add): Merge conflict in .gitignore
 Automatic merge failed; fix conflicts and then commit the result.

Option 2: unstage, stash, clone, unstash, and then commit

The alternative (and longer) way of fixing the fatal: refusing to merge unrelated histories issues is to unstage your current commits, stash them, clone your required remote repository, and then place your stashed branch contents into the new clone.

This will ensure that any conflicts that you may encounter in the code are addressed before merging and prevent application errors from occurring.
To unstage all the files in your last commit, use the following git command: git reset HEAD~.

To stash your unsaved files, use the following git command: git stash.

This will give you a clean working tree to pull your remote repository into. Once you’ve successfully pulled into your branch, you can unstash your files, commit them as a separate commit and resolve any file conflicts that you may have.

To unstash your files, use git pop. This will move the changes stashed and reapplies them to your current working copy.

Alternatively, you can use git stash apply to add the changes to your current working copy of code.

Here is a quick summary of differences between git stash apply and <code”>git pop:

• git pop: ‘pops’ the changes from the stash and applies them to the current code
• git stash apply: keeps the changes in the stash and applies the changes to the current code

How to prevent ‘fatal: refusing to merge unrelated histories’

The easiest way to prevent the fatal: refusing to merge unrelated histories error is to avoid pulling remote repositories into branches that already have commits on them.
However, sometimes you just want to keep the commits. One way to prevent the error is to create a brand new branch, pull your required code in, and then manually merge your local branch into your main flow.

Here is a git example of the flow:

# branch A is where your current code is
# clone in your remote repo into a new and separate branch. 
# For our purposes, it's branch B
 ​
git clone -b [branch] [remote_repo]
 ​
# to merge A into B, you need to be on B
# merge your branches together
git merge A

The only thing about merges is that if there is a conflict in the code, there is no way around it other than resolving it as usual.
Here’s what your merge branch looks like on Git:

          C1---C2---C3 branch A
                      
  Ca---Cb---Cc---Ce---Cf branch B

Kubernetes Troubleshooting with Komodor

The above guide should help you through the troubleshooting steps you need to follow in order to resolve the fatal: refusing to merge unrelated histories Git error.

This is, of course, just one of many Git errors that you may come across in your K8s logs. Such deceptively minor and often easy-to-miss issues can cause serious issues and detecting them could be time-consuming, stressful, and often downright impossible.

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After using Git for a while, you’ll notice that there’s a lot of mistakes that can be difficult to fix. This isn’t the case with the fatal: refusing to merge unrelated histories error. Unlike a number of other errors, this issue has one solution that you can reuse whenever you encounter it.

In this guide, we’re going to talk about how to solve the fatal: refusing to merge unrelated histories errors in Git. Let’s get started!

Why Does the Error Occur?

The error fatal: refusing to merge unrelated histories occurs when two unrelated projects are merged into a single branch. This error arises because each project has its own history of commits and tags. These two histories will be incompatible with each other.

There are two main scenarios when this error may arise.

When you create a new repository, make a few commits, and try to pull from another remote repository, this error can occur. This error will be displayed because the local repository with which you are working will have a different history to the project which you are trying to retrieve.

You may encounter this error if the .git directory inside a project that has been deleted or corrupted. In this case, the Git command line may not be able to read your local project’s history.

When you try to push data to or pull data from a remote repository, this error will occur. This is because Git doesn’t know if the remote repository is compatible with your current repository.

How to Solve ‘fatal: refusing to merge unrelated histories’

We’ve done enough talking. To solve this issue, you can use the --allow-unrelated-histories flag when pulling data from a repository:

Git pull origin master –allow-unrelated-histories

You’ll want to substitute origin with the remote repository from which you are pulling resources. You should replace master with the branch that you want to retrieve.

This command was added to handle the rare event that you are working with two projects that have their own branches. 

Alternatively, you could clone a new version of the remote repository using git clone and start over. However, this is not usually necessary.

You can read more about the –allow-unrelated-histories flag on the official Git documentation.

Conclusion

The fatal: refusing to merge unrelated histories error occurs when either a .git directory is unreadable or when you are trying to pull data from a repository with its own commit history. This error tells you that you are trying to Git merge two unrelated projects to the same work tree.

Now you’re ready to solve this error using the –allow-unrelated-histories flag like an expert!

1. Common Scenarios of the fatal: refusing to merge unrelated histories Error in Git
2. Resolve the fatal: refusing to merge unrelated histories Error in Git

This article outlines the steps needed to solve the fatal: refusing to merge unrelated histories error in Git. We usually encounter such an error when attempting to merge two unrelated Git projects into one branch.

It will pop up when the recipient branch has commits, and the clone has incompatible tags.

Here are some cases where you will likely encounter the fatal: refusing to merge unrelated histories error in Git.

1. You have a local repository containing commits and attempt to pull from an existing remote repository. Since the histories are different, Git does not know how to proceed.

   Hence the error message.

2. Your .git directory is corrupted.

3. When your branches are at different HEAD positions.

We can resolve the error by allowing unrelated merging. We can do this by adding the --allow-unrelated-histories flag to the pull request, as shown below.

$ git pull origin master --allow-unrelated-histories

Git will allow you to merge branches with unrelated histories. It is pretty easy if your files do not conflict.

The above method is the easiest; however, there is a longer route to the same destination.

First, you will have to unstage all your current commits and stash them. You can then pull from the remote repo and apply the stash to the new clone.

This makes it easier to deal with merge conflicts in case they occur.

To unstage, all the files in the last commit, use the command below.

Run the command below to stash the files.

Now you have a clean working tree, and you can run a pull request, after which you will unstash and apply the stashed changes to the working tree. You can run:

The command above will apply the stash and discard it. If you want to apply and keep the stash, you can run:

With that being said, what is the easiest way to avoid this error message?

Avoid pulling remote repositories into local branches containing commits. If you have to, create a new branch and manually pull and merge the changes.

In conclusion, the fatal: refusing to merge unrelated histories error occurs when we are attempting to merge branches with different commit histories. We have gone through the two ways to resolve the error and how to best avoid it.