Git Rebase vs. Merge: The Difference Between Them and When to Use Each

Overview

In Git, both git merge and git rebase are methods used to integrate changes from one branch into another. Although both achieve the goal of integrating changes, they do so in entirely different ways. Understanding the difference between them is crucial for effectively managing your Git history, especially when working with multiple branches and contributors.

Key points we’ll cover:

• What is git merge and how it works.
• What is git rebase and how it works.
• Pros and cons of each approach.
• The key differences between git merge and git rebase.
• When to use git merge vs. git rebase.

Summary of Differences:

• git merge: Integrates branches with a merge commit, preserving the full history of both branches.
• git rebase: Re-applies commits from one branch onto another, rewriting the commit history and creating a linear sequence of commits.

1. What Is git merge?

git merge is used to combine the changes from one branch into another. This method keeps the histories of both branches intact by creating a merge commit, which reflects both branches' changes.

How git merge works

When you use git merge, Git finds the common ancestor between the branches, compares the changes made since that point, and then attempts to combine those changes into a new merge commit.

For example, if you want to merge your feature-branch into main:

# Switch to the main branch
git checkout main

# Merge feature-branch into main
git merge feature-branch

After this command, the main branch will have a new merge commit that combines the changes from feature-branch while preserving both branches’ individual commit histories.

Pros of git merge:

• Complete history: You can always trace the exact point where branches were merged.
• Non-destructive: The original commits and their histories remain intact.
• Collaborative: Great for large teams where the branch history is important for understanding contributions.

Cons of git merge:

• Messier history: Frequent merges result in a lot of merge commits, leading to a more complex history.
• Merge commits: These commits can clutter the history when you merge often, making the history harder to read.

2. What Is git rebase?

git rebase is another method for integrating changes from one branch into another, but it works differently than git merge. Instead of creating a merge commit, git rebase re-applies your commits from the feature branch onto the target branch (such as main), as if those commits were made after the latest commits in the target branch.

How git rebase works

When you run git rebase, Git moves the base of your feature branch to the latest commit on the target branch, effectively rewriting the history of your branch.

For example, to rebase feature-branch onto main:

# Switch to the feature branch
git checkout feature-branch

# Rebase the feature branch onto the main branch
git rebase main

This command will replay the commits from feature-branch on top of the latest commit from main, creating a linear history as if the feature branch was started from the latest state of main.

Pros of git rebase:

• Clean, linear history: No merge commits cluttering the history.
• Easier to follow: A linear history is easier to read, which can simplify debugging and tracing changes.

Cons of git rebase:

• Rewrites history: Rewriting history can be problematic when working in teams, especially if the branch has already been pushed to a shared repository.
• Conflict handling: You may need to resolve conflicts multiple times when rebasing.

3. Key Differences Between git merge and git rebase

The fundamental difference between git merge and git rebase lies in how they integrate the changes and how they affect your Git history.

More detailed breakdown:

• Commit History:
  • Merge: The history retains a non-linear structure with a merge commit. This means you can see when a branch diverged from main and when it was merged back in.
  • Rebase: The history is rewritten to create a straight line of commits. After a rebase, it appears as if the feature branch was always up-to-date with main.
• Linear vs. Non-linear History:
  • Merge: Maintains the natural divergence and convergence of branches. The history shows where branches split and later came together.
  • Rebase: Creates a linear sequence of commits, making it look like the feature branch was always based on the latest state of the target branch.
• Merge Conflicts:
  • Merge: You resolve conflicts once, at the point of merging.
  • Rebase: Conflicts can arise at each step as Git re-applies each commit on top of the new base, so you might need to resolve conflicts multiple times.

4. When to Use git merge

Use git merge when:

• You’re working with a team on shared or public branches (like main or develop). The merge commit provides a full history of all branches, which is valuable for collaboration.
• Preserving history is important: Merging retains the full history of both branches, showing exactly when and how the branches were merged.
• You want to keep your workflow simple: Since git merge is non-destructive and doesn’t rewrite history, it’s often safer in collaborative environments.

Example:

Let’s say you're working on a feature in feature-branch and it's time to integrate your changes into the main branch. You can use git merge to combine the two branches without altering the history of either branch.

git checkout main
git merge feature-branch

5. When to Use git rebase

Use git rebase when:

• You want to maintain a clean, linear history: If you’re working on a feature branch and you don’t want to clutter the history with merge commits, rebase can help you achieve a simpler, linear commit history.
• You're working solo or in small teams: When fewer people are working on the project, and you're confident that rewriting history won’t cause issues, rebase can be a good choice.
• You want to tidy up before a pull request: Rebasing your feature branch onto main before opening a pull request ensures your branch is up-to-date without any merge commits.

Example:

You're working on feature-branch and want to integrate the latest changes from main before opening a pull request. You can rebase to make sure your commits are applied cleanly on top of the most recent main branch changes.

git checkout feature-branch
git rebase main

Absolutely! Let me reformat the post into the previous style, where the content outline and high-level explanation are presented at the top, and then we dive into the detailed explanation for each section.

Conclusion

The choice between git merge and git rebase depends on your workflow, team size, and preferences. Both are powerful tools in Git, but they serve different purposes.

• Use git merge when you want to keep a detailed and complete history of all changes, especially in collaborative environments.
• Use git rebase when you want a clean, linear history, particularly when working on feature branches that have not been shared with others yet.

Understanding the difference between these two commands will help you manage your Git repositories more effectively and choose the right tool for the right situation.

Further Reading:

• Official Git Documentation on Merging
• Official Git Documentation on Rebasing