Rebase vs merge mental model in Git - When to Use Which

The Big Idea

Ever wondered why developers choose rebase or merge to combine their work without chaos?

The Scenario

Imagine you and your friend are writing a story together, but you both write different chapters separately. Now, you want to combine your chapters into one book.

The Problem

If you just copy and paste chapters without order, the story might be confusing or have repeated parts. Doing this by hand takes a lot of time and can cause mistakes.

The Solution

Using rebase or merge in Git helps combine your work smoothly. Merge keeps all chapters as they are but joins them together, while rebase rewrites your chapters to fit perfectly after your friend's, making the story flow better.

Before vs After

✗ Before

copy chapters manually
paste chapters in random order

✓ After

git merge feature-branch
or
git rebase main

What It Enables

It lets teams combine their work clearly and efficiently, avoiding confusion and keeping history clean.

Real Life Example

A developer finishes a new feature while others update the main project. Using rebase or merge helps add the feature without breaking the project or losing work.

Key Takeaways

Manual combining is slow and error-prone.

Merge joins work preserving all history.

Rebase rewrites history for a cleaner story.

Practice

1. What is the main difference between git merge and git rebase?

easy

A. git merge rewrites commit messages; git rebase preserves commit messages.

B. git merge deletes the source branch; git rebase deletes the target branch.

C. git merge only works on remote branches; git rebase only works on local branches.

D. git merge combines histories preserving all commits; git rebase rewrites history to create a linear sequence.

Solution

1. Step 1: Understand git merge behavior

   git merge combines two branches by creating a new commit that preserves the history of both branches without changing existing commits.

2. Step 2: Understand git rebase behavior

   git rebase moves or reapplies commits from one branch onto another, rewriting history to make it look like a straight line.

3. Final Answer:

   git merge combines histories preserving all commits; git rebase rewrites history to create a linear sequence. -> Option D

4. Quick Check:

   Merge preserves history, rebase rewrites it [OK]

Hint: Merge keeps history; rebase rewrites it linearly [OK]

Common Mistakes:

• Thinking merge deletes branches
• Believing rebase only works on remote branches
• Confusing which command rewrites history

2. Which of the following is the correct syntax to rebase the current branch onto main?

easy

A. git rebase main

B. git merge main

C. git rebase origin/main

D. git checkout main && git rebase

Solution

1. Step 1: Identify the command to rebase current branch

   The command git rebase main rebases the current branch onto the main branch.

2. Step 2: Check other options for correctness

   git merge main merges, not rebases; git rebase origin/main rebases onto remote tracking branch which may be outdated; git checkout main && git rebase is invalid syntax.

3. Final Answer:

   git rebase main -> Option A

4. Quick Check:

   Rebase current branch onto main = git rebase main [OK]

Hint: Use 'git rebase branch-name' to rebase current branch [OK]

Common Mistakes:

• Using merge instead of rebase
• Rebasing onto remote branch without fetching
• Incorrect chaining of commands

3. Given the following commands executed in order on branch feature:

git checkout feature
git rebase main
git log --oneline --graph

What will the commit history look like compared to using git merge main instead?

medium

A. A linear history with feature commits on top of main commits.

B. A merge commit combining main and feature histories.

C. No change in history; feature branch remains separate.

D. Feature branch commits are deleted.

Solution

1. Step 1: Understand effect of git rebase main on feature branch

   Rebasing moves feature commits to be based on the latest main commits, creating a straight, linear history.

2. Step 2: Compare with git merge main effect

   Merging creates a new merge commit that combines histories, preserving the branch structure and showing a branch point.

3. Final Answer:

   A linear history with feature commits on top of main commits. -> Option A

4. Quick Check:

   Rebase = linear history; merge = merge commit [OK]

Hint: Rebase = linear history; merge = merge commit [OK]

Common Mistakes:

• Thinking rebase creates merge commits
• Believing history stays unchanged after rebase
• Assuming commits are deleted after rebase

4. You ran git rebase main on your feature branch but got conflicts. After resolving conflicts, which command should you run to continue the rebase?

medium

A. git commit -m 'resolved conflicts'

B. git merge --continue

C. git rebase --continue

D. git rebase --abort

Solution

1. Step 1: Identify the correct command to continue rebase after conflicts

   After resolving conflicts during a rebase, git rebase --continue tells Git to proceed with applying remaining commits.

2. Step 2: Understand other options

   git merge --continue is for merge conflicts, not rebase; git commit -m is manual commit but rebase expects --continue; git rebase --abort cancels the rebase.

3. Final Answer:

   git rebase --continue -> Option C

4. Quick Check:

   Continue rebase after conflicts = git rebase --continue [OK]

Hint: Use 'git rebase --continue' after resolving conflicts [OK]

Common Mistakes:

• Using merge commands during rebase
• Trying to commit manually instead of continuing
• Aborting instead of continuing rebase

5. You want to update your feature branch with the latest changes from main but keep a clean, linear history without merge commits. Which sequence of commands achieves this safely?

hard

A. git checkout feature; git merge origin/main

B. git checkout feature; git fetch origin; git rebase origin/main

C. git checkout main; git pull; git checkout feature; git merge main

D. git checkout feature; git pull origin main

Solution

1. Step 1: Fetch latest changes from remote main branch

   git fetch origin updates local remote tracking branches without changing working branches.

2. Step 2: Rebase feature branch onto updated origin/main

   git rebase origin/main reapplies feature commits on top of latest main commits, keeping history linear and clean.

3. Final Answer:

   git checkout feature; git fetch origin; git rebase origin/main -> Option B

4. Quick Check:

   Fetch then rebase for clean update [OK]

Hint: Fetch first, then rebase onto remote main for clean history [OK]

Common Mistakes:

• Merging instead of rebasing for linear history
• Pulling directly on feature branch causing merge commits
• Not fetching latest remote changes before rebase