Git Merge vs Rebase: How to Choose

Whether you‘re new to Git or have years of experience, understanding the differences between git merge and git rebase is key for any developer. When should you merge branches? When is it better to rebase instead?

This comprehensive guide will explain what rebase and merge do, the key differences, and – most importantly – provide clear guidance on when each method makes the most sense.

By the end, you‘ll have the confidence to navigate branch merging like a Git pro!

How Branching and Merging Works in Git

Before we dive into specifics on merging vs rebasing, let‘s step back and define a few key concepts…

What‘s a Commit?

A commit is a snapshot of your project at a point in time, recorded inside Git:

For example, saving three files will create one commit. Inside it is metadata like the author, date, and a description of the changes.

What are Branches?

Branches represent independent lines of development.

The main branch (usually called master) contains official production-ready code. While new development and features get built in separate branches copied from master:

These branch off, allowing work to happen in isolation without impacting the live site.

What‘s Merging?

Merging takes changes on one branch and integrates them into another:

Once your feature branch is ready, it gets merged back into master so those code changes go live.

The next sections will explore the two ways of merging:

1. git merge
2. git rebase

Both aim to integrate branches, but in very different ways.

Git Merge vs Rebase: How Are They Different?

Let‘s compare how git merge and git rebase work to see the key differences:

	Git Merge	Git Rebase
Branch history	Preserved	Rewritten
Commit chronology	Out of order	Linearized
Feature branch	Retained	Deleted

Git Merge

Merging with git merge joins multiple sequences of commits into one unified history:

           Branch A              Branch B

         a1 - a2 - a3        b1 - b2 - b3   

               \                /      

                 merge commit   

                  a1 - a2 - a3 - b1 - b2 - b3

The feature branch history gets appended intact onto master, preserving all commits. The result can end up out of chronological sequence, since the merges intermix different lines of development.

Git Rebase

The git rebase command transfers commits to another branch by rewriting history:

         Branch A                   Branch B

      a1 - a2 - a3           b1 - b2 - b3   

(Rebase b onto a)

                a1 - a2 - a3 - b1 - b2 - b3  

It takes all changes from Branch B and replays them onto the end of Branch A. This results in a linear, chronological sequence of commits.

But Branch B‘s history gets overwritten since the old commits are deleted. Only the newly rebased set appears.

The most noticeable difference comes down to whether project history is preserved or rewritten.

The Pros and Cons of Merging vs Rebasing

Given those key differences, let‘s explore the specific advantages and disadvantages of each approach…

Benefits of Git Merge

• Preserves context: Retains chronological history of all branches merged, so you can easily track when and how each change occurred.
• Visibility: Developers can view feature branch work separately before integration.
• Traceability: Bugs can be traced back to the exact commit that introduced them.
• Undoability: Merges are easy to undo since no history gets overwritten.
• Collaboration: Shared branches can be merged without team members losing work or getting overwritten.

Tradeoffs of Git Merge

• Messy history: Multiple diverging branches intermixing can clutter commit logs over time.
• No linear order: Jumping between different lines of development makes project history confusing to follow.
• Merge conflicts: Occasional merge conflicts happen that developers must resolve before merging.

Advantages of Git Rebase

• Clean history: Rebasing rewrites history for a linear, simplified timeline of changes.
• No superfluous merges: These add noise without context, which rebase avoids.
• Conflict resolution: Rebasing lets you fix conflicts immediately after they‘re introduced.
• Up-to-date: Bringing latest commits from master ensures you rebase from the current codebase.

Drawbacks of Git Rebase

• Destructive: The original commits get overwritten, which can cause work and context to be lost.
• Hard to undo: After rewrite, reinstating dropped commits becomes extremely tricky.
• No complete history: Only the rebased commits remain, earlier changes get erased.
• Remote disruption: Rebasing should only happen on local branches since rewriting shared history can overwrite team member‘s work.

When Should You Merge or Rebase?

Now that you understand the upsides and downsides of each approach, how do you decide which method to use?

When to Git Merge

Branches are shared or public – If multiple developers collaborate on a branch, use merging to cleanly bring changes together without disrupting other‘s work.

History context is critical – For easy tracking of when and how changes occurred across parallel branches.

Teams are large or remote – Merging is preferable for large complex teams coordinating across many branches.

When to Git Rebase

Simplified history needed – Rebasing results in a straight timeline ideal for understanding progression of changes.

Private local branches – Rebasing your own feature branches causes no disruption, cleanly bringing work up-to-date with master.

Frequent updates needed – Repeatedly rebase on master to incorporate others‘ ongoing work.

Long-running branches – Before merging back a complex branch that‘s been open a while, rebasing cleans up clutter.

Using Git Merge and Rebase Together

The best practice is to leverage both rebasing and merging in concert:

Keep your own feature branches tidy through rebasing. But allow external team branches to cleanly merge so you don‘t disrupt other‘s work. Some examples:

• For your local branches, rebase frequently to resolve issues and keep updated with master.

• Utilize interactive rebasing to squash messy commits like "fix typo", "oops", etc.

• Merge team-shared branches to bring changes together without affecting commit history others rely on.

This staged workflow plays to the strengths of both approaches:

Other Key Considerations

• What is your team‘s git skill level? Less experienced developers may want to avoid rebase complexity.

• Implement access controls for rebase capabilities if needed. In GitHub, claim-based SSH protects the push-force ability needed.

• Always back up branches before rebasing as a safety net for rollback.

Conclusion: Should You Merge or Rebase?

Deciding between merging and rebasing depends largely on your specific team workflows. Small teams may lean toward rebasing for clean commit history. While large external teams gravitate to merging to avoid disrupting other‘s work.

But every team and project is unique. By understanding the key differences covered here, you can tailor an integration strategy that makes the most sense for your needs.

The main thing is having flexibility through mastering both approaches. Rebase locally and merge publicly. Utilize their respective benefits, and you’ll smoothly bring collaborative changes together!

I hope this guide has demystified the merge vs rebase dilemma for you once and for all. Let me know if you have any other questions!