What is `git rebase` and How is it Different from `git merge`?

Git is one of the most popular version control systems used by developers worldwide. It provides a wide range of tools to manage the history of code changes, and among these tools, git rebase and git merge are two of the most commonly used commands. Both commands serve the purpose of integrating changes from one branch into another, but they do so in different ways. In this article, we will explain what git rebase is, how it works, and how it differs from git merge.

Understanding Git Rebase

git rebase is a powerful command in Git used to integrate changes from one branch into another. Unlike git merge, which creates a new commit that combines changes from both branches, git rebase rewrites the commit history. It effectively moves or “re-applies” commits from one branch onto another, resulting in a linear history.

When you run git rebase, Git will take all the commits from the current branch and replay them on top of the target branch. This operation ensures that the commit history remains clean and linear. It is often used to update a feature branch with the latest changes from the main branch without creating unnecessary merge commits.

Git Rebase Example

Let’s take a look at a simple example to better understand how git rebase works:

git checkout feature-branch
git rebase main

In this example, the feature-branch is rebased onto the main branch. After running this command, Git will reapply the commits from feature-branch onto the top of the main branch, effectively rewriting history.

Understanding Git Merge

git merge is another essential Git command used to combine changes from one branch into another. Unlike git rebase, which rewrites history, git merge creates a new commit, called a “merge commit,” that combines the changes from both branches while preserving their individual histories.

When you run git merge, Git looks at the common ancestor of both branches and creates a new commit that merges the changes from both branches into the current branch. This process retains the individual commit histories of both branches, and no commits are rewritten.

Git Merge Example

Here’s a simple example of how git merge works:

git checkout main
git merge feature-branch

In this case, the changes from feature-branch are merged into the main branch, creating a new merge commit that combines the changes from both branches. The history of both branches is preserved in the merge commit.

Key Differences Between Git Rebase and Git Merge

Now that we’ve explored both git rebase and git merge, let’s look at their key differences:

  • History Rewriting: One of the most significant differences between git rebase and git merge is how they handle commit history. git rebase rewrites commit history, while git merge creates a merge commit that preserves the history of both branches.
  • Merge Commits: With git merge, a new merge commit is created every time you merge branches, which can clutter the commit history. On the other hand, git rebase avoids this by keeping the history linear.
  • Use Case: git rebase is typically used when you want a clean, linear history. It’s useful for feature branches that are being updated with the latest changes from the main branch. git merge, however, is preferred when you want to maintain the context of the branches being merged, as it preserves the commit history of both branches.
  • Conflict Resolution: When conflicts arise during a rebase, you need to resolve them commit by commit. In contrast, with a merge, you resolve conflicts all at once during the merge commit process.
  • Safety: git merge is often considered safer because it does not alter commit history, while git rebase can cause issues if used improperly, especially in shared branches.

When to Use Git Rebase vs Git Merge

Both git rebase and git merge are useful tools, but the choice between them depends on the situation and the desired outcome.

When to Use Git Rebase

  • When you want a clean and linear project history.
  • When working with feature branches and regularly integrating changes from the main branch.
  • When collaborating with a team on a shared repository where a clean history is preferred.
  • When working on your own branches and you want to keep the history concise without the clutter of merge commits.

When to Use Git Merge

  • When you want to preserve the history of both branches.
  • When working on a shared branch where rewriting history could cause issues for others.
  • When merging long-running branches that have diverged significantly.
  • When you want to keep a record of when branches were merged together.

Conclusion

Both git rebase and git merge are essential tools in Git that allow developers to integrate changes from one branch into another. The primary difference lies in how they handle commit history: git rebase rewrites the commit history to create a linear history, while git merge preserves the history of both branches by creating a merge commit. Choosing between the two depends on the project requirements and your workflow.

In general, if you prefer a clean, linear history and are working on feature branches, git rebase is a great choice. However, if you need to preserve the context of both branches and work in a collaborative environment, git merge is the safer and more straightforward option.

Whether you use git rebase or git merge, understanding the differences and knowing when to use each command is key to managing your Git workflow effectively. Experiment with both commands to find which best fits your development process.