Git Merge vs Rebase: Which Is Better for Your Workflow?

Introduction Git Merge vs Rebase

Two common Git workflows to integrate changes between branches are merging and rebasing. While both combine changes, there are fundamental differences between Git merge and rebase. In this guide, we will understand how merge and rebase work in Git and illustrate their usage with examples.

How Git Merge Works

The git merge command lets you integrate changes from a source branch into a target branch. For example, merging feature branch changes into main:

git checkout main
git merge feature

This creates a new “merge commit” in main that combines the feature branch changes:

    A---B---C main
   /        
D---E---F---G feature

git merge feature

                    A---B---C---M main
                   /           /
D---E---F---G---/           feature

The resulting merge commit M includes changes from both branches.

Merge Types

Git handles merges intelligently based on commit relationships between branches:

Fast-forward merge – If target branch contains no commits after the merge point, the source branch HEAD is simply moved forward:

A---B---C---D main
      \
       E---F---G feature
           
git checkout main
git merge feature 

         A---B---C---D---E---F---G main
                    \
                     feature

3-way merge – If both branches have diverged, their snapshots are combined and a merge commit is created:

    A---B---X main
   /
C---D---E---F---G feature

git checkout main
git merge feature

                A---B---X---M main
               /           /  
C---D---E---F---G-------/  feature

This replayability of commits makes Git history branching interaction explicit.

How Git Rebase Works

Rebasing essentially replays a branch’s commits on top of another specified base branch. For example, rebasing feature onto main:

A---B---C main
  \ 
   D---E---F feature

git checkout feature
git rebase main

                      A---B---C main
                     /
D'--E'--F' feature

This moves the entire feature branch to begin on top of main, creating new commits D’, E’, F’.

How Rebase Works

Rebase replays commits from the current branch individually on top of the specified base branch:

• Checkout the feature branch
• Find the common ancestor between feature and main (commit A)
• Replay each commit after A from feature on top of main in order
  • Apply D atop main and create D’
  • Apply E atop D’ and create E’
  • Apply F atop E’ and create F’
• Update feature to point to F’

This can cause conflicts if the replayed commits cannot be cleanly applied atop the base branch.

Key Differences Between Merge and Rebase

Merging preserves complete history whereas rebasing rewrites history.

When to Use Merge or Rebase

Use merge when:

• You want to integrate upstream changes into your feature branch.
• You need a clean project history.
• Multiple developers are collaborating on the branch.

Use rebase when:

• You want a linear project history without unnecessary merges.
• You work alone on the feature branch most of the time.
• The branch is still private and unpushed to remote.

Rebasing rewrites history so avoid it on public branches that others may depend on.

Frequently Asked Questions

1. What happens in a git merge vs rebase?

Merge creates a merge commit while rebase replays commits onto another base branch.

2. When should you use rebase over merge?

If you need a linear project history, rebase locally before pushing your feature branch.

3. Does rebasing rewrite commit history?

Yes, rebasing changes commit SHAs so avoid it on public branches.

4. What is the golden rule of rebasing?

Never rebase commits that have been shared publicly.

5. How do you abort a rebase?

Run git rebase --abort to abort an ongoing rebase process and restore original state.

Conclusion

• git merge integrates branches by creating merge commits.
• git rebase replays commits from one branch onto another.
• Merging preserves history while rebasing rewrites it.
• Understand the difference between the two workflows.
• Leverage both merge and rebase as suitable for the situation.

Mastering merging and rebasing gives greater flexibility in integrating changes between branches.