Version control systems are all about managing contributions between multiple distributed authors ( usually developers ). Sometimes multiple developers may try to edit the same content. If Developer A tries to edit code that Developer B is editing a conflict may occur. To alleviate the occurrence of conflicts developers will work in separate isolated branches. Thegit merge command's primary responsibility is to combine separate branches and resolve any conflicting edits.
Understanding merge conflicts
Merging and conflicts are a common part of the Git experience. Conflicts in other version control tools like SVN can be costly and time-consuming. Git makes merging super easy. Most of the time, Git will figure out how to automatically integrate new changes.
Conflicts generally arise when two people have changed the same lines in a file, or if one developer deleted a file while another developer was modifying it. In these cases, Git cannot automatically determine what is correct. Conflicts only affect the developer conducting the merge, the rest of the team is unaware of the conflict. Git will mark the file as being conflicted and halt the merging process. It is then the developers' responsibility to resolve the conflict.
Types of merge conflicts
A merge can enter a conflicted state at two separate points. When starting and during a merge process. The following is a discussion of how to address each of these conflict scenarios.
Git fails to start the merge
A merge will fail to start when Git sees there are changes in either the working directory or staging area of the current project. Git fails to start the merge because these pending changes could be written over by the commits that are being merged in. When this happens, it is not because of conflicts with other developer's, but conflicts with pending local changes. The local state will need to be stabilized using git stash, git checkout, git commit or git reset. A merge failure on start will output the following error message:
error:Entry'<fileName>'notuptodate.Cannotmerge.(Changesinworkingdirectory)Git fails during the merge
A failure DURING a merge indicates a conflict between the current local branch and the branch being merged. This indicates a conflict with another developers code. Git will do its best to merge the files but will leave things for you to resolve manually in the conflicted files. A mid-merge failure will output the following error message:
error:Entry'<fileName>'wouldbeoverwrittenbymerge.Cannotmerge.(Changesinstagingarea)Creating a merge conflict
In order to get real familiar with merge conflicts, the next section will simulate a conflict to later examine and resolve. The example will be using a Unix-like command-line Git interface to execute the example simulation.
$mkdirgit-merge-test
$cdgit-merge-test
$gitinit.
$echo"thisissomecontenttomesswith">merge.txt
$gitaddmerge.txt
$gitcommit-am"wearecommitingtheinitalcontent"
[main(root-commit)d48e74c]wearecommitingtheinitalcontent
1filechanged,1insertion(+)
createmode100644merge.txtThis code example executes a sequence of commands that accomplish the following.
- Create a new directory named
git-merge-test,change to that directory, and initialize it as a new Git repo. - Create a new text file
merge.txtwith some content in it. - Add
merge.txtto the repo and commit it.
Now we have a new repo with one branch mainand a file merge.txt with content in it. Next, we will create a new branch to use as the conflicting merge.
$gitcheckout-bnew_branch_to_merge_later
$echo"totallydifferentcontenttomergelater">merge.txt
$gitcommit-am"editedthecontentofmerge.txttocauseaconflict"
[new_branch_to_merge_later6282319]editedthecontentofmerge.txttocauseaconflict
1filechanged,1insertion(+),1deletion(-)The proceeding command sequence achieves the following:
- create and check out a new branch named
new_branch_to_merge_later - overwrite the content in
merge.txt - commit the new content
With this new branch: new_branch_to_merge_later we have created a commit that overrides the content of merge.txt
gitcheckoutmain
Switchedtobranch'main'
echo"contenttoappend">>merge.txt
gitcommit-am"appendedcontenttomerge.txt"
[main24fbe3c]appendedcontenttomerge.tx
1filechanged,1insertion(+)This chain of commands checks out the mainbranch, appends content to merge.txt, and commits it. This now puts our example repo in a state where we have 2 new commits. One in the mainbranch and one in the new_branch_to_merge_later branch. At this time lets git merge new_branch_to_merge_later and see what happen!
$gitmergenew_branch_to_merge_later
Auto-mergingmerge.txt
CONFLICT(content):Mergeconflictinmerge.txt
Automaticmergefailed;fixconflictsandthencommittheresult.BOOM 💥. A conflict appears. Thanks, Git for letting us know about this!
How to identify merge conflicts
As we have experienced from the proceeding example, Git will produce some descriptive output letting us know that a CONFLICT has occcured. We can gain further insight by running the git status command
$gitstatus
Onbranchmain
Youhaveunmergedpaths.
(fixconflictsandrun"gitcommit")
(use"gitmerge--abort"toabortthemerge)Unmergedpaths:
(use"gitadd<file>..."tomarkresolution)
bothmodified:merge.txt
The output from git status indicates that there are unmerged paths due to a conflict. The merge.text file now appears in a modified state. Let's examine the file and see whats modified.
$catmerge.txt
<<<<<<<HEAD
thisissomecontenttomesswith
contenttoappend
=======
totallydifferentcontenttomergelater
>>>>>>>new_branch_to_merge_laterHere we have used the cat command to put out the contents of the merge.txtfile. We can see some strange new additions
<<<<<<< HEAD=======>>>>>>> new_branch_to_merge_later
Think of these new lines as "conflict dividers". The ======= line is the "center" of the conflict. All the content between the center and the <<<<<<< HEAD line is content that exists in the current branch mainwhich the HEAD ref is pointing to. Alternatively all content between the center and >>>>>>> new_branch_to_merge_later is content that is present in our merging branch.
How to resolve merge conflicts using the command line
The most direct way to resolve a merge conflict is to edit the conflicted file. Open the merge.txt file in your favorite editor. For our example lets simply remove all the conflict dividers. The modified merge.txt content should then look like:
thisissomecontenttomesswith
contenttoappend
totallydifferentcontenttomergelaterOnce the file has been edited use git add merge.txt to stage the new merged content. To finalize the merge create a new commit by executing:
gitcommit-m"mergedandresolvedtheconflictinmerge.txt"Git will see that the conflict has been resolved and creates a new merge commit to finalize the merge.
Git commands that can help resolve merge conflicts
General tools
gitstatusThe status command is in frequent use when a working with Git and during a merge it will help identify conflicted files.
gitlog--mergePassing the --merge argument to the git log command will produce a log with a list of commits that conflict between the merging branches.
gitdiffdiff helps find differences between states of a repository/files. This is useful in predicting and preventing merge conflicts.
Tools for when git fails to start a merge
gitcheckoutcheckout can be used for undoing changes to files, or for changing branches
gitreset--mixedreset can be used to undo changes to the working directory and staging area.
Tools for when git conflicts arise during a merge
gitmerge--abortExecuting git merge with the --abort option will exit from the merge process and return the branch to the state before the merge began.
gitresetGit reset can be used during a merge conflict to reset conflicted files to a know good state
Summary
Merge conflicts can be an intimidating experience. Luckily, Git offers powerful tools to help navigate and resolve conflicts. Git can handle most merges on its own with automatic merging features. A conflict arises when two separate branches have made edits to the same line in a file, or when a file has been deleted in one branch but edited in the other. Conflicts will most likely happen when working in a team environment.
There are many tools to help resolve merge conflicts. Git has plenty of command line tools we discussed here. For more detailed information on these tools visit stand-alone pages for git log, git reset, git status, git checkout, and git reset. In addition to the Git, many third-party tools offer streamlined merge conflict support features.
FAQs
How do I resolve merge conflicts in git? ›
The easiest way to resolve a conflicted file is to open it and make any necessary changes. After editing the file, we can use the git add a command to stage the new merged content. The final step is to create a new commit with the help of the git commit command. Git will create a new merge commit to finalize the merge.
How do I create a merge conflict in git? ›- Create a new directory named git-merge-test, change to that directory, and initialize it as a new Git repo.
- Create a new text file merge. txt with some content in it.
- Add merge. txt to the repo and commit it.
Merge conflicts happen when you merge branches that have competing commits, and Git needs your help to decide which changes to incorporate in the final merge. Git can often resolve differences between branches and merge them automatically.
How do I resolve merge conflicts in a pull request? ›- On your local computer, you can use the git diff command to find the conflicts between the two branches and make changes to resolve them. ...
- In the console, you can choose Resolve conflicts.
The simplest way, if you have unmerged paths, use git merge --abort to abort the merge. This way your code will look the same as it was before trying to merge with some other branch...
How to resolve merge conflicts in git without commit? ›- Step 1: Switch to Git Repository. ...
- Step 2: Generate and Update File. ...
- Step 3: Track File. ...
- Step 4: Push Changes to Git Repository. ...
- Step 5: Update File. ...
- Step 6: Git Stash. ...
- Step 7: Modify Existing File. ...
- Step 8: Staged Add Changes.
To do a merge (locally), git checkout the branch you want to merge INTO. Then type git merge <branch> where <branch> is the branch you want to merge FROM. Because the history of master and the history of make_function share common ancestors and don't have any divergence descendents, we get a "fast-forward" merge.
How do I manually merge in git? ›To merge branches locally, use git checkout to switch to the branch you want to merge into. This branch is typically the main branch. Next, use git merge and specify the name of the other branch to bring into this branch. This example merges the jeff/feature1 branch into the main branch.
How to merge two users in git? ›- - Fill out the required fields, typing the name of the repository to confirm and entering the new owner's GH username:
- - New owner receives an email with an auth token that expires after 24 hours. ...
- - Click on Emails in the left sidebar > Add email address field > Add new email:
- Talk directly. Assuming that there is no threat of physical violence, talk directly to the person with whom you have the problem. ...
- Choose a good time. ...
- Plan ahead. ...
- Don't blame or name-call. ...
- Give information. ...
- Listen. ...
- Show that you are listening. ...
- Talk it all through.
What is a 3 way merge in git? ›
At its core, a three-way merge is technically any kind of merge involving two divergences from a merge base. 3-Way Merge Scheme. In other words, whenever a three-way merge is performed, the common ancestor of two distinct versions of a file or codebase is used as the base of the merge operation itself.
How do I merge a branch to master? ›- git fetch.
- git rebase origin/master.
- git checkout master.
- git pull origin master.
- git merge test.
- git push origin master.
On GitHub.com, navigate to the main page of the repository. Under your repository name, click Pull requests. In the "Pull Requests" list, click the pull request you would like to add to a merge queue. Click Merge when ready to add the pull request to the merge queue.
What is a merge conflict? ›A merge conflict occurs when a version of a file has been submitted that is newer than the version of the file you have started to base your changes on.
How to identify merge conflicts in Git? ›To see the beginning of the merge conflict in your file, search the file for the conflict marker <<<<<<< . When you open the file in your text editor, you'll see the changes from the HEAD or base branch after the line <<<<<<< HEAD .
How do I continue merge after resolving conflicts? ›- switch to experimental branch (git checkout experimental)
- make a bunch of changes.
- commit it (git commit -a)
- switch to master branch (git checkout master)
- make some changes and commit there.
- move to “branch”: git checkout branch.
- merge “master” in “branch”: git merge master.
If there were uncommitted worktree changes present when the merge started, git merge --abort will in some cases be unable to reconstruct these changes. It is therefore recommended to always commit or stash your changes before running git merge.
How do I accept all incoming changes in git merge conflict? ›- Accept the local version. To accept all changes on a file from the local version, run: git checkout --ours <file name> ...
- Accept the remote version. To update the changes on a file from the remote branch, run: git checkout --theirs <file name> ...
- Review changes individually.
- --no-ff : a merge commit will be created in all cases, even if the merge could be resolved as a fast-forward.
- --ff-only : the merge will be resolved only if it is possible to fast-forward.
How do I merge changes from one branch to another? ›
Merge branches
In the Branches popup (main menu Git | Branches) or in the Branches pane of the Git tool window, select the target branch that you want to integrate the changes to, and choose Checkout from the context menu to switch to that branch.
All git does in the master branch is to move the HEAD pointer in the master branch to the latest commit from the “dev” branch. Once the merge is done, make sure to do a git push, to push your changes to the remote repository.
How to merge two unrelated branches in git? ›But this doesn't mean that Git cannot perform any merge. In fact, all you need to do to merge unrelated branches is to use the flag --allow-unrelated-histories . This tells Git to combine all the files and commits of both unrelated branches into one branch, as long as there are no file conflicts.
How to merge from master to branch in git? ›- Git installed (see how to install Git on Ubuntu, macOS, Windows, CentOS 7, or CentOS 8). ...
- Run the following command to rebase the branch: git rebase master.
- Resolve any conflicts that arise and the rebase is complete. ...
- Resolve any merge conflicts that arise and complete the merge.
Merge logic
Normally, a commit is something that you create, typically by editing files in the working tree, adding them to the index, and then saying git commit . But when you ask it to merge one branch into another, Git itself is generating a commit — the merge commit.
git merge-file is useful for combining separate changes to an original. Suppose <base-file> is the original, and both <current-file> and <other-file> are modifications of <base-file> , then git merge-file combines both changes. If there are conflicts, the user should edit the result and delete one of the alternatives.
Can we merge two feature branches in git? ›Merge branches
Merging your branch into master is the most common way to do this. Git creates a new commit (M) that is referred to as a merge commit that results from combining the changes from your feature branch and master from the point where the two branches diverged.
Actually yes you totally can, when you merge again it will bring over any commits that don't exist on production.
What are the 4 ways to resolve conflicts? ›- Communicate. Open communication is key in a dispute. ...
- Actively Listen. Listen to what the other person has to say, without interrupting. ...
- Review Options. Talk over the options, looking for solutions that benefit everyone. ...
- End with a Win-Win Solution.
- Don't Ignore Conflict. ...
- Clarify What the Issue Is. ...
- Bring Involved Parties Together to Talk. ...
- Identify a Solution. ...
- Continue to Monitor and Follow Up on the Conflict.
What are 5 common ways to handle conflict? ›
- Accommodation. This is a lose/win situation. ...
- Compromise. ...
- Avoidance. ...
- Competition. ...
- Collaboration.
The Workings of Git Rebase and Merge
In the process, rebase flattens the history, removing unwanted entries. Git merge, on the other hand, only changes the target branch and creates a commit, preserving the history of the source branch.
What is git rebase? Rebasing is the process of moving or combining a sequence of commits to a new base commit. Rebasing is most useful and easily visualized in the context of a feature branching workflow.
How to merge three commits into one? ›- Steps to merging multiple commits. Running git rebase in interactive mode. Typing "squash" Choosing between commit messages. Pushing changes.
- Squashing.
- Related Resources.
A Git pull request is essentially the same as a Git merge request. Both requests achieve the same result: merging a developer's branch with the project's master or main branch. Their difference lies in which site they are used; GitHub uses the Git pull request, and GitLab uses the Git merge request.
Does merging delete a branch? ›In a good workflow, the feature branch is deleted once its merged back into master. New branches should be created for each new feature(s) that you work on.
How do I merge a branch into another branch VS code? ›In the Source Control View, select Branch Merge Branch from in the view menu. Select addPowerOperation . In the History View, select Merge in the context menu of the branch which contains the conflicting commit. This merges the content of this branch into the master branch.
What is a pull request in git? ›In their simplest form, pull requests are a mechanism for a developer to notify team members that they have completed a feature. Once their feature branch is ready, the developer files a pull request via their Bitbucket account.
What happens when we merge a branch to master? ›When you perform a merge, you effectively merge one branch into another—typically a feature branch or bug fix branch into a main branch such as master or develop. Not only will the code changes get merged in, but also all the commits that went into the feature branch.
Can we revert a merge commit? ›How to Undo a Merge Commit in Git. You can use the Git reset command to undo a merge. Firstly, you need to check for the commit hash (or id) so you can use it to go back to the previous commit. To check for the hash, run git log or git reflog .
How do I rollback a merge request? ›
- On the top bar, select Main menu > Projects and find your project.
- On the left sidebar, select Merge requests and identify your merge request.
- Scroll to the merge request reports area, and find the report showing when the merge request was merged.
- Select Revert.
Merge Commits are unique commits automatically generated by CI providers to run tests against the resulting code of merging tip of pull request into tip of base branch.
What are the 4 types of conflict? ›- Data Conflicts.
- Relationship Conflicts.
- Value Conflicts.
- Structural Conflicts.
It's the responsibility of the person who wants to merge. Obviously any changes that would have caused conflicts would have been reviewed before being merged, and if a change caused an unreasonable number of conflicts it would have been rejected.
How to merge in git command? ›To merge branches locally, use git checkout to switch to the branch you want to merge into. This branch is typically the main branch. Next, use git merge and specify the name of the other branch to bring into this branch. This example merges the jeff/feature1 branch into the main branch.
How do I merge master to current branch? ›- Git installed (see how to install Git on Ubuntu, macOS, Windows, CentOS 7, or CentOS 8). ...
- Run the following command to rebase the branch: git rebase master.
- Resolve any conflicts that arise and the rebase is complete. ...
- Resolve any merge conflicts that arise and complete the merge.
- Think it over. Honestly assess the situation. ...
- Figure out what you want to say and how to say it. Don't blame others. ...
- Really listen. Listen carefully to what is being said, and if you don't understand what is being said, ask clarifying questions. ...
- Work toward understanding.
To see the beginning of the merge conflict in your file, search the file for the conflict marker <<<<<<< . When you open the file in your text editor, you'll see the changes from the HEAD or base branch after the line <<<<<<< HEAD .
What triggers a merge conflict? ›A merge conflict occurs when a version of a file has been submitted that is newer than the version of the file you have started to base your changes on. In this blog, we look at what merge conflicts are, how they happen in Git, and how you can avoid them with a few simple tips to streamline your development.
What are the two ways to merge in git? ›Git merging combines sequences of commits into one unified history of commits. There are two main ways Git will merge: Fast Forward and Three way. Git can automatically merge commits unless there are changes that conflict in both commit sequences.
How to merge two commits into one in git? ›
- Steps to merging multiple commits. Running git rebase in interactive mode. Typing "squash" Choosing between commit messages. Pushing changes.
- Squashing.
- Related Resources.
Merge lets you merge different Git branches. Rebase allows you to integrate the changes from one branch into another. Merge logs show you the complete history of commit merging. Rebase logs are linear. As the commits are rebased, the history is altered to reflect this.
How to check difference between two git branches? ›In order to compare two branches easily, you have to use the “git diff” command and provide the branch names separated by dots. Using this command, Git will compare the tip of both branches (also called the HEAD) and display a “diff” recap that you can use to see modifications.
How to rebase a branch in git? ›To rebase, make sure you have all the commits you want in the rebase in your master branch. Check out the branch you want to rebase and type git rebase master (where master is the branch you want to rebase on).