Rebase vs merge mental model in Git - Visual Side-by-Side Comparison

Process Flow - Rebase vs merge mental model

Start: Branch A and Branch B diverged

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Option 1: Merge

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Create a new merge commit

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Branches combined with history preserved

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End

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Option 2: Rebase

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Move Branch B commits on top of Branch A

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Rewrite Branch B history

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Linear history without merge commit

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End

Shows two ways to combine branches: merge creates a new commit joining histories, rebase moves commits to create a straight line.

Execution Sample

Git

git checkout feature
# Option 1: git merge main
# Option 2: git rebase main

Switch to feature branch, then either merge main into it or rebase feature onto main.

Process Table

Step	Action	Branch State Before	Branch State After	Result
1	Start with main and feature branches diverged	main: A-B-C feature: A-B-D-E	main: A-B-C feature: A-B-D-E	Branches diverged at commit B
2	Merge main into feature	feature: A-B-D-E	feature: A-B-D-E-M	New merge commit M combines C and E
3	Feature branch now has merge commit	feature: A-B-D-E-M	feature: A-B-D-E-M	History shows branching and merging
4	Reset feature branch to before merge	feature: A-B-D-E-M	feature: A-B-D-E	Prepare for rebase
5	Rebase feature onto main	feature: A-B-D-E	feature: A-B-C-D'-E'	Commits D and E replayed on top of C as D' and E'
6	Feature branch has linear history	feature: A-B-C-D'-E'	feature: A-B-C-D'-E'	No merge commit, history looks like a straight line
7	End	feature: A-B-C-D'-E'	feature: A-B-C-D'-E'	Branches combined by rebase or merge

💡 Execution stops after feature branch is updated by merge or rebase.

Status Tracker

Variable	Start	After 2 (merge)	After 5 (rebase)	Final
feature branch commits	A-B-D-E	A-B-D-E-M	A-B-C-D'-E'	A-B-C-D'-E'

Key Moments - 3 Insights

Why does merge create a new commit but rebase does not?

Merge combines histories by creating a new commit (row 2), while rebase moves commits to a new base, rewriting history without a merge commit (row 5).

What does it mean that rebase rewrites history?

Rebase creates new commits (D' and E') with the same changes but different parent commits, making history linear (row 5), unlike merge which preserves original commits.

When should I prefer merge over rebase?

Use merge to keep full history and show branch structure (row 3). Use rebase to keep history clean and linear (row 6).

Visual Quiz - 3 Questions

Look at the execution table, what is the feature branch state after step 2?

A A-B-D-E-M (with a merge commit)

B A-B-C-D'-E' (rebased commits)

C A-B-D-E (unchanged)

D A-B-C (main branch only)

💡 Hint

Check the 'Branch State After' column at step 2 in the execution table.

At which step does the feature branch history become linear?

A Step 2

B Step 5

C Step 3

D Step 1

💡 Hint

Look for when commits D and E are replayed on top of C as D' and E' in the execution table.

If you want to keep the branch history showing all merges, which command would you use?

A git rebase main

B git merge main

C git reset main

D git checkout main

💡 Hint

Refer to the action in step 2 where a merge commit is created.

Concept Snapshot

Rebase vs Merge in Git:
- Merge combines branches by creating a new commit.
- Rebase moves commits to a new base, rewriting history.
- Merge preserves branch history and shows merges.
- Rebase creates a linear history without merge commits.
- Use merge for shared branches, rebase for clean history.

Full Transcript

This visual shows how Git combines branches using merge or rebase. Initially, main and feature branches diverge at commit B. Using merge, a new commit M joins the histories, preserving the branch structure. Using rebase, commits from feature are moved on top of main's latest commit C, creating new commits D' and E' and a straight history line. Merge keeps all commits and shows the branch split and join. Rebase rewrites commits to make history linear without merge commits. Choose merge to keep full history or rebase to keep history clean.