Understanding Git Merging
Merging in Git refers to the act of integrating modifications from one branch into another. It is typically performed once work on a branch is finalized and ready to be incorporated elsewhere. Git examines the commit history from both branches and evaluates how to combine them. When no divergence exists between them, Git applies a fast-forward merge by simply advancing the branch pointer. When both branches include unique commits, Git performs a three-way merge, generating a new commit that unites the changes. This process preserves a clean and trackable history while enabling simultaneous development.
Git includes several merge approaches depending on how branches evolve. The most common strategies are fast-forward merges and three-way merges, which are explained below.
Fast-Forward Merging
A fast-forward merge happens when the branch receiving updates has not recorded new commits since the other branch was created. Git does not produce a merge commit in this scenario. Instead, it advances the branch pointer directly. The result is a simple, linear history, though it does not explicitly indicate that work was completed on a separate branch.
Three-Way Merging
A three-way merge occurs when both branches have progressed independently. Git locates their shared ancestor and compares it with the latest commits on each branch. It then generates a merge commit that integrates both sets of changes. This method is valuable in collaborative environments because it preserves context and clearly documents when two development paths were combined.
The Short Answer Version
If you already understand how merging works and only require the essential steps, use the following commands to merge one branch into another.
# Switch to the branch you want to merge into
$ git checkout target-branch
# Pull the latest changes from the remote
$ git pull origin target-branch
# Merge the source branch into the current branch
$ git merge source-branch
# Commit the merge if it’s not auto-committed
$ git commit -m “Merge changes from source-branch”
# Push the merged branch to the remote repository
$ git push origin target-branch
Merge Branches In Git
Merging branches is a central part of collaborative Git workflows. You often create a new branch, build and test your changes independently, and then merge those updates back into another branch when everything is ready. Follow the steps below to merge branches successfully.
Create a New Branch
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$ git checkout -b feature-branch
This command creates a branch named feature-branch and switches to it. You will use this branch to implement and test your adjustments.
Pull the Latest Changes
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$ git checkout target-branch
$ git pull origin target-branch
Always pull the most recent updates before merging. This ensures you start from a clean base and reduces the chances of unplanned conflicts.
Merge the Branch
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$ git merge feature-branch
Git decides which merge strategy to apply based on the commit history. If the target branch contains no new commits, Git performs a fast-forward merge. If both branches have diverged, Git performs a three-way merge. When no conflicts appear, Git completes the merge automatically; when conflicts do appear, Git pauses and requests that you resolve them manually.
Commit the Merged Changes
If conflicts occur or edits must be applied manually, Git will not automatically generate a merge commit. After resolving all issues, add a clear, descriptive commit message.
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$ git commit -m “merge feature-branch into target-branch”
Push the Merged Branch
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$ git push origin target-branch
This step completes the merge, and the updates are now available in the target-branch.
Resolve Merge Conflicts
Merge conflicts occur when Git cannot automatically reconcile overlapping modifications in the same file. Git highlights the conflict sections so that you can resolve them manually.
Identify the Conflict Files
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$ git status
Git lists the files containing conflicts. Look for files marked as modified in both branches. These require manual resolution.
Open and Resolve Conflicts
Open the affected files in your editor. Git marks conflicting sections using the symbols <<<<<<<, =======, and >>>>>>>. Select which modifications to keep, remove the markers, and adjust the file so it represents your final desired version.
Commit and Push the Changes
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$ git add .
$ git commit -m “Resolve merge conflicts”
$ git push origin target-branch
After resolving and committing the changes, your integrated code is pushed to the remote repository.
Conclusion
You have learned how to merge branches in Git using both fast-forward and three-way merging strategies, how to address merge conflicts, and how to finalize the merge by committing and pushing your updates. These skills are fundamental for developers collaborating on shared codebases. If you are new to Git branching or want a refresher.
