Git refusing to merge unrelated histories on rebase

Question

During git rebase origin/development the following error message is shown from Git:

fatal: refusing to merge unrelated histories
Error redoing merge 1234deadbeef1234deadbeef

My Git version is 2.9.0. It used to work fine in the previous version.

How can I continue this rebase allowing unrelated histories with the forced flag introduced in the new release?

Answer 1

You can use --allow-unrelated-histories to force the merge to happen.

The reason behind this is that default behavior has changed since Git 2.9:

"git merge" used to allow merging two branches that have no common base by default, which led to a brand new history of an existing project created and then get pulled by an unsuspecting maintainer, which allowed an unnecessary parallel history merged into the existing project. The command has been taught not to allow this by default, with an escape hatch --allow-unrelated-histories option to be used in a rare event that merges histories of two projects that started their lives independently.

See the Git release changelog for more information.

More information can be found in this answer.

Answer 2

In my case, the error was just fatal: refusing to merge unrelated histories on every try, especially the first pull request after remotely adding a Git repository.

Using the --allow-unrelated-histories flag worked with a pull request in this way:

git pull origin branchname --allow-unrelated-histories

As per 2.9.0 release notes - git pull has been taught to pass the --allow-unrelated-histories option to underlying git merge

Answer 3

Try the following command:

git pull origin master --allow-unrelated-histories

This should solve your problem.

Answer 4

I got this error when I set up a local repository first. Then I went to GitHub and created a new repository. Then I ran

git remote add origin <repository url>

When I tried to push or pull, I got the same fatal: unrelated_histories error every time.

Here is how I fixed it:

git pull origin master --allow-unrelated-histories
git merge origin origin/master
... add and commit here...
git push origin master

Answer 5

1. Solve the problem

Following the error when doing a git pull origin master:

fatal: refusing to merge unrelated histories

Run one of the below commands

 # It could be master
 git pull origin master --allow-unrelated-histories

 # Or main
 git pull origin main --allow-unrelated-histories

 # Or just try with origin
 git pull origin main --allow-unrelated-histories

If it opens the nano editor you can just save and close with Ctrl + X.

Now push the changes on local

 git push

Error during merge or Error on other git operations

Keep in mind that this error could happen in other operation performed between 2 different branches. For instance when trying to merge 2 branches which don't have related history which makes sense.

Eitherway, simply add --allow-unrelated-histories should again, do the trick

git merge some_branch --allow-unrelated-histories

---

2. Meaning

• The error:

The “fatal: refusing to merge unrelated histories” Git error occurs when two unrelated projects are merged (i.e., projects that are not aware of each other’s existence and have mismatching commit histories).

• The get-merge command (from Git documentation): --allow-unrelated-histories:

  --allow-unrelated-histories

By default, git merge command refuses to merge histories that do not share a common ancestor. This option can be used to override this safety when merging histories of two projects that started their lives independently. As that is a very rare occasion, no configuration variable to enable this by default exists and will not be added.

---

References

• Recommended: “The “fatal: refusing to merge unrelated histories” Git error
• Git 2.9 Release Notes

---

More on Stack Overflow

• Recommended A great explanation and warning on using --allow-unrelated-histories: ”refusing to merge unrelated histories” failure while pulling to recovered repository
• If --allow-unrelated-histories don't work: "fatal: refusing to merge unrelated histories" after adding a Git remote
• Git is refusing to merge unrelated histories. What are 'unrelated histories'?
• This user uses GitHub Desktop: How can I fix "refusing to merge unrelated histories" when uploading a project to GitHub?
• Git failed with a fatal error, refusing to merge unrelated histories with Git push

Answer 6

For this, enter the command:

git pull origin branchname --allow-unrelated-histories

For example,

git pull origin master --allow-unrelated-histories

Reference:

GitHub unrelated histories issue

Answer 7

I ran this command and the issue got resolved.

git pull origin branchName --allow-unrelated-histories

Check out this page for more information.

Answer 8

I had the same problem. Try this:

git pull origin master --allow-unrelated-histories 

git push origin master

Answer 9

Try git pull --rebase development

Answer 10

For Android Studio and IntelliJ:

First, commit everything and resolve any conflicts.

Then open the terminal from below of IDE and enter:

git pull origin master --allow-unrelated-histories

Now you can push.

Answer 11

Since all the other answers are not actually answering the question, here is a solution inspired by this answer on a related question.

So you get your error doing git rebase:

$ git rebase origin/development
fatal: refusing to merge unrelated histories
Error redoing merge 1234deadbeef1234deadbeef

This error doesn't actually cancel the rebase, but you are now in the middle of it:

$ git status
interactive rebase in progress; onto 4321beefdead
Last command done (1 command done):
   pick 1234deadbeef1234deadbeef test merge commit

So you can now do the merge by hand. Find out the parent commits of the original merge commit:

$ git log -1 1234deadbeef1234deadbeef
commit 1234deadbeef1234deadbeef
Merge: 111111111 222222222
Author: Hans Dampf
Date:   Wed Jun 6 18:04:35 2018 +0200

    test merge commit

Find out which of the two merge parents is the one that was merged into the current one (probably the second one, verify with git log 222222222), and then do the merge by hand, copying the commit message of the original merge commit:

$ git merge --allow-unrelated 222222222 --no-commit
Automatic merge went well; stopped before committing as requested
$ git commit -C 1234deadbeef1234deadbeef
[detached HEAD 909af09ec] test merge commit
 Date: Wed Jun 6 18:04:35 2018 +0200
$ git rebase --continue
Successfully rebased and updated refs/heads/test-branch.

Answer 12

Warning: This will potentially overwrite the remote repository

This worked for me:

git push origin master --force

Answer 13

Firstly, pull the remote changes to your local using the following command:

git pull origin branchname --allow-unrelated-histories

** branchname is master in my case.

When the pull command is done, the conflict occurs. You should solve the conflicts. I use Android Studio to solve conflicts.

When the conflicts are solved, the merge is done!

Now you can safely push.

Answer 14

I had the same problem. The problem is remote had something preventing this.

I first created a local repository. I added a LICENSE and README.md file to my local and committed.

Then I wanted a remote repository so I created one on GitHub. Here I made a mistake of checking "Initialize this repository with a README", which created a README.md in remote too.

So now when I ran

git push --set-upstream origin master

I got:

error: failed to push some refs to 'https://github.com/lokeshub/myTODs.git'
hint: Updates were rejected because the tip of your current branch is behind
hint: its remote counterpart. Integrate the remote changes
(e.g. hint: 'git pull ...') before pushing again.
hint: See the 'Note about fast-forwards' in 'git push --help' for details.

Now to overcome this I did

git pull origin master

Which resulted in the below error:

From https://github.com/lokeshub/myTODs
branch            master     -> FETCH_HEAD
fatal: refusing to merge unrelated histories**

I tried:

git pull origin master --allow-unrelated-histories

Result:

From https://github.com/lokeshub/myTODs
 * branch            master     -> FETCH_HEAD
Auto-merging README.md
CONFLICT (add/add): Merge conflict in README.md
Automatic merge failed;
fix conflicts and then commit the result.

Solution:

I removed the remote repository and created a new (I think only removing file README could have worked) and after that the below worked:

git remote rm origin
git remote add origin https://github.com/lokeshub/myTODOs.git
git push --set-upstream origin master

Answer 15

This usually happens when you commit first time to remote repository. As error clearly says "refusing to merge unrelated histories", we need to use --allow-unrelated-histories flag.

git pull origin master  --allow-unrelated-histories

Now there would be some conflicts which we have to solve manually. After that just commit the code and push it.

Answer 16

When doing a git pull, I got this message fatal: refusing to merge unrelated histories for a repo module where I hadn't updated the local copy for a while.

I ran this command just to refresh local from origin. I just wanted latest from remote and didn't need any local changes.

git reset --hard origin/master

This fixed it in my case.

Answer 17

I tried git pull --allow-unrelated-histories, and it didn't work, but this solved the issue for me:

1. I copied all the files on my desktop repository to another folder and then deleted the folder.

2. Then I clone the repository again because it is a new project.

3. When I copied my files again and push it worked like charm.

Answer 18

I struggled with this as well, but I managed to find a workaround.

When you run into the error above, just cherry-pick the merge commit and then continue the rebase:

git cherry-pick -m 1 1234deadbeef1234deadbeef
git rebase --continue

Answer 19

If you created a new repository on GitHub and accidentally initialized it with README or .gitignore files.

If you found yourself unable to merge or rebase because .git folder got corrupted.

Then:

• Create a new folder
• git clone
• Paste all your files into this folder

Now the local and remote will have "related histories" and will merge or rebase happily.

Answer 20

The error is resolved by toggling the allow-unrelated-histories switch. After a Git pull or Git merge command, add the following tag:

git pull origin master --allow-unrelated-histories

After then, maybe you will get a conflict. So resolve the conflict, and commit it. It worked for me.

Answer 21

I run into the same issue:

This is what I've done:

git pull origin main --allow-unrelated-histories

I used Visual Studio Code to resolve merge conflicts, and then I did:

git commit -m "commit message"

git push origin main

Answer 22

For my case I wanted to merge an unrelated history branch to my current:

git merge <-unrelated-history-branch-name> --allow-unrelated-histories

Answer 23

blue112's answer doesn't solve this question, which is in the context of rebasing.

The only way to synchronize the two diverged branches is to merge them back together, resulting in an extra merge commit and two sets of commits that contain the same changes (the original ones, and the ones from your rebased branch). Needless to say, this is a very confusing situation.

So, before you run git rebase, always ask yourself, “Is anyone else looking at this branch?” If the answer is yes, take your hands off the keyboard and start thinking about a non-destructive way to make your changes (e.g., the git revert command). Otherwise, you’re safe to re-write history as much as you like.

Reference: The Golden Rule of Rebasing

Answer 24

If someone is facing the same problem while rebase the branch after doing --allow-unrelated-histories also please use this git pull origin <branch-name> --allow-unrelated-histories --no-ff hope it may help someone

Answer 25

This also happens if you have a shallow Git clone of the repository.

I recently encountered this problem in my CI/CD setup, and none of the previous solutions worked for me. I was building a CI/CD pipeline to analyze code on MR creation against the MR source branch. For that, I needed to run an analysis on the main branch once and then on the MR source branch merged with main, and I got this error while trying to merge branches via the git merge command.

The reason for this happening in the CI/CD setup: Usually in a CI/CD environment, Git repositories are a shallow clone to speed up things, which doesn't include a full history of commits due to which, when merging Git, we may think that we are trying to merge unrelated branches which is in fact not true.

Solution:

Convert a shallow repository to an unshallow one using the following command:

git fetch --unshallow

Answer 26

A pretty rare scenario I believe; You have removed the remote (e.g. origin):

git remote rm origin

Then, after a while, for some reason, you tried to add it back but entered the wrong URL.

git remote add origin [email protected]:example/wrong.git

The solution of course is to use the right URL:

git remote add origin [email protected]:example/correct.git

Answer 27

I am using the rebase for years and I had never encountered such a problem. However, your first problem is, that you try to do it directly on the remote branch development from the remote repository, called origin. That is literally wrong because rebase is a dangerous command, that restructures the git history. Having said that, you should first try on your local repository and pushing it only, if it works for you as expected.

So, my usual rebase workflow looks like following (but please keep in mind, that you should not use rebase on branches, which you are not the only one committee. For such branches, use simply merge and resolve conflicts, if applicable):

1. make sure you have a clean working tree (no uncommit changes)
2. checkout to the branch you want to rebase onto (for instance, let's say it's master; as a one-line command): git checkout master && git pull origin master && git checkout development
3. Do the actual rebase: git rebase master
4. If it's done and everything works as expected, push it to your remote. For doing so, you need to force it, because the remote host already has the history in another order, the remote would answer with nothing to push. So, we need to say "my local version of the history is correct, overwrite everything on that remote branch using my local version of the history": git push -f origin development

As I already mentioned, keep in mind, that rebase manipulates the git history, that is usually a bad thing. However, it's possible to do that on branches, where no one else commits to. In order to keep the branch pull-able for the other developers, use another merge strategy like merge itself, squash or cherrypick. So, in other words: Rebase shouldn't be your tool on distributed development. It works fine for you if you are the only one who works on this repository.

We use the feature branch strategy. In this, I usually use rebase in order to get the "updates" from the other developers, that happened in the meantime on the master branch. Doing so, it reduces the size of commits that are visible in a pull request. Therefore, it makes it easier for the code reviewer to see my changes made in this feature branch.

Answer 28

I faced this error after force-pushing to origin/master a development branch with a few hundreds of commits, by the Administrator, on the server side.

Well, I just didn't wanted to pull (fetch+merge), but just to align my local master to the remote origin master. Moving to a separate folder and doing a Git clone is one approach, but I believe it is more elegant solution just to do a hard reset.

So my answer to this error, in this particular case, is none of the above.

I just wanted this:

git reset --hard origin/master

Answer 29

fatal: refusing to merge unrelated histories may also be caused by a shallow clone, because the graft commit doesn't go far enough down to see the common base.

Answer 30

I had the same error, and this command worked for me:

git pull gitlab master --allow-unrelated-histories

Note that gitlab might be origin or heroku in your case.