Rebase vs Merge When to Use Each and Why

Introduction#

Version control is essential in modern software development, and Git provides two primary methods to integrate changes from one branch into another: merge and rebase. While both achieve the goal of combining changes, they work differently and are suited for different scenarios. Understanding when to use each method helps maintain a clean and efficient Git history.

What is Merging?#

Merging integrates changes from one branch into another by creating a merge commit that connects the histories of both branches. This preserves the commit history as it originally happened, making it easy to track changes.

Example of a Merge Workflow#

Suppose you are working on a feature branch based on main.
The main branch receives updates while you are developing the feature.
To bring those updates into your feature branch, you run:
```
git checkout feature
git merge main
```
Git creates a new merge commit that combines both histories.

Pros of Merging#

Preserves commit history - Shows exactly when branches diverged and merged.
No history rewriting - Commit hashes remain unchanged, making it safe for shared branches.
Clearer collaboration - Useful when multiple developers work on the same branch.

Cons of Merging#

Messy commit history - Each merge adds a new commit, which can clutter history.
Complex conflicts - If branches have diverged significantly, resolving conflicts can be difficult.

What is Rebasing?#

Rebasing moves the commits of one branch on top of another, effectively rewriting history. Instead of merging two commit histories, it reapplies your branch's commits as if they were made after the latest commit on the target branch.

Example of a Rebase Workflow#

You have a feature branch based on an older version of main.
The main branch has received new commits.
To update your feature branch without a merge commit, run:
```
git checkout feature
git rebase main
```
Git reapplies your commits from feature on top of the latest main.
If conflicts occur, Git pauses the rebase for manual resolution.
Once resolved, continue with:
```
git rebase --continue
```

Pros of Rebasing#

Clean commit history - Eliminates unnecessary merge commits, making history linear and easier to read.
Better for feature branches - Keeps work isolated and allows a smooth merge into main.
Easier debugging - A linear history simplifies git bisect and identifying when bugs were introduced.

Cons of Rebasing#

Rewrites history - Changing commit hashes can cause issues if others are working on the same branch.
Risky for shared branches - Should not be used on branches that others have already pulled.
Conflict resolution can be tedious - If there are many conflicts, rebasing can become a manual process.

When to Use Merge vs. Rebase#

Scenario	Use Merge?	Use Rebase?
Keeping a feature branch up-to-date with `main`	No	Yes
Merging a completed feature into `main`	Yes	No
Collaborative branches (multiple devs)	Yes	No
Cleaning up a private branch before merging	No	Yes
Resolving a long-lived, diverged branch	Yes	No

Best Practices#

Use merge for shared branches (e.g., merging feature into main).
Use rebase to keep a feature branch up-to-date before merging.
Never rebase public/shared branches - rewriting history affects others.
Use git pull --rebase instead of git pull to maintain a clean, linear history.
Use git log --oneline --graph to visualize how merge and rebase affect history.

Conclusion#

Both merge and rebase have their place in a Git workflow. If you prioritize keeping a detailed history with all merge points, use merge. If you prefer a clean and linear history, use rebase, but be cautious when rewriting history. Understanding these techniques will help you maintain a clean, efficient Git workflow while collaborating effectively with your team.