Why rebasing creates linear history in Git - Visual Breakdown

Process Flow - Why rebasing creates linear history

Start with branch feature

↓

Identify commits on feature

↓

Find base commit on main

↓

Reapply feature commits on top of main

↓

Result: feature branch commits follow main commits

↓

Linear history achieved

Rebasing takes your feature commits and places them on top of the latest main branch commits, making the commit history a straight line.

Execution Sample

Git

git checkout feature
git rebase main

This moves the feature branch commits to be after the latest commits on main, creating a linear history.

Process Table

Step	Action	Current HEAD	Resulting Commit History
1	Checkout feature branch	feature	main -> A -> B (feature commits)
2	Start rebase onto main	feature	main -> A -> B (to be reapplied)
3	Reapply commit A on main	feature	main -> A -> B main -> A' (rebased)
4	Reapply commit B on A'	feature	main -> A -> B main -> A' -> B' (rebased)
5	Rebase complete	feature	main -> A' -> B' (linear history)

💡 All feature commits reapplied on top of main, creating a linear commit history.

Status Tracker

Variable	Start	After Step 3	After Step 4	Final
HEAD	feature	A' (commit A rebased)	B' (commit B rebased)	B' (feature branch tip)
Commit History	main -> A -> B	main -> A -> B main -> A'	main -> A -> B main -> A' -> B'	main -> A' -> B'

Key Moments - 2 Insights

Why do the commit hashes change after rebasing?

Because rebasing creates new commits with the same changes but different parent commits, so the hashes are new, as shown in steps 3 and 4 of the execution_table.

Does rebasing change the main branch commits?

No, main branch commits remain unchanged; only the feature branch commits are reapplied on top of main, preserving main's history as shown in the commit history column.

Visual Quiz - 3 Questions

Look at the execution_table at step 4, what is the commit history?

A feature -> A -> B

B main -> A' -> B'

C main -> A -> B

D main -> B' -> A'

💡 Hint

Check the 'Resulting Commit History' column at step 4 in the execution_table.

At which step does the HEAD point to the rebased commit B'?

A Step 4

B Step 2

C Step 3

D Step 5

💡 Hint

Look at the 'Current HEAD' column in the execution_table and variable_tracker after step 4.

If you do not rebase but merge instead, how would the commit history differ?

A It would delete feature branch commits

B It would be linear like rebasing

C It would create a merge commit, making history non-linear

D It would rewrite main branch commits

💡 Hint

Rebasing reapplies commits linearly, merging creates a new commit joining histories, see concept_flow for linear history.

Concept Snapshot

git rebase <branch>
- Moves your commits on top of another branch
- Creates new commits with new hashes
- Results in a straight, linear commit history
- Keeps main branch unchanged
- Useful for clean project history

Full Transcript

Rebasing in git takes your feature branch commits and reapplies them on top of the latest commits from the main branch. This process creates new commits with new hashes because the parent commits change. The main branch commits remain unchanged. The result is a linear history where your feature commits appear as if they were made after the main branch commits, making the project history easier to read. This is different from merging, which creates a merge commit and keeps the history branching. The commands 'git checkout feature' and 'git rebase main' perform this operation. The execution table shows each step: checking out the feature branch, starting the rebase, and replaying each commit on top of main, ending with a linear commit history.

Practice

1. What is the main reason rebasing creates a linear history in Git?

easy

A. It creates a new branch automatically

B. It merges all branches into one commit

C. It deletes all previous commits

D. It moves your commits on top of the latest commit from the target branch

Solution

1. Step 1: Understand what rebasing does

   Rebasing takes your commits and places them on top of another branch's latest commit, replaying them in order.

2. Step 2: Effect on commit history

   This action removes the branching structure by making your commits appear as if they were made after the latest commit on the target branch, creating a straight line.

3. Final Answer:

   It moves your commits on top of the latest commit from the target branch -> Option D

4. Quick Check:

   Rebase = replay commits on top [OK]

Hint: Rebase replays commits on latest branch commit [OK]

Common Mistakes:

• Thinking rebase merges commits into one
• Believing rebase deletes old commits
• Confusing rebase with branch creation

2. Which Git command syntax correctly rebases the current branch onto main?

easy

A. git merge main

B. git rebase main

C. git rebase -m main

D. git checkout main rebase

Solution

1. Step 1: Identify the correct rebase command

   The correct syntax to rebase the current branch onto main is git rebase main.

2. Step 2: Check other options for errors

   git merge main merges instead of rebasing; git rebase -m main is invalid syntax; git checkout main rebase is not a valid command.

3. Final Answer:

   git rebase main -> Option B

4. Quick Check:

   Rebase syntax = git rebase branch [OK]

Hint: Use 'git rebase branchname' to rebase [OK]

Common Mistakes:

• Using merge instead of rebase
• Adding invalid flags like -m
• Combining checkout and rebase incorrectly

3. Given this commit history:

main: A --- B --- C
feature: A --- B --- D --- E

After running git rebase main on feature, what will the new commit history look like?

medium

A. main: A --- B --- Cfeature: A --- B --- C --- D' --- E'

B. main: A --- B --- Cfeature: D --- E

C. main: A --- B --- C --- D --- Efeature: A --- B --- C --- D --- E

D. main: A --- B --- Cfeature: A --- B --- D --- E

Solution

1. Step 1: Understand rebase effect on commits

   Rebasing feature onto main moves commits D and E to be based on C, replaying them as new commits D' and E'.

2. Step 2: Visualize new commit history

   The main branch remains unchanged. The feature branch now appears as if commits D' and E' were made after C, creating a linear history.

3. Final Answer:

   main: A --- B --- C
   feature: A --- B --- C --- D' --- E' -> Option A

4. Quick Check:

   Rebase = replay commits on main tip [OK]

Hint: Rebase replays commits after target branch tip [OK]

Common Mistakes:

• Assuming commits stay unchanged
• Thinking rebase merges commits
• Ignoring that rebased commits get new IDs

4. You tried to rebase your branch but got a conflict error. What is the best way to fix this and continue the rebase?

medium

A. Abort the rebase and start over with git rebase --abort

B. Run git merge --continue to resolve conflicts

C. Fix the conflicts manually, then run git rebase --continue

D. Delete the branch and create a new one

Solution

1. Step 1: Understand rebase conflict handling

   When a conflict occurs during rebase, Git pauses and lets you fix conflicts manually in the files.

2. Step 2: Continue rebase after fixing conflicts

   After resolving conflicts, you must run git rebase --continue to proceed with the rebase process.

3. Final Answer:

   Fix the conflicts manually, then run git rebase --continue -> Option C

4. Quick Check:

   Fix conflicts + git rebase --continue [OK]

Hint: Fix conflicts then run 'git rebase --continue' [OK]

Common Mistakes:

• Using merge commands during rebase
• Aborting instead of continuing after fix
• Deleting branch unnecessarily

5. You have two feature branches, feature1 and feature2, both branched from main. feature1 was rebased onto main and pushed. Now you want to rebase feature2 onto feature1. What is the main benefit of this approach?

hard

A. It creates a linear history combining both features without merge commits

B. It deletes feature1 branch automatically

C. It merges feature2 into main directly

D. It resets feature2 to main ignoring feature1

Solution

1. Step 1: Understand rebasing one feature branch onto another

   Rebasing feature2 onto feature1 places feature2's commits on top of feature1, making the history linear.

2. Step 2: Benefit of linear history

   This avoids merge commits and shows a clear sequence of changes, making history easier to read and understand.

3. Final Answer:

   It creates a linear history combining both features without merge commits -> Option A

4. Quick Check:

   Rebase feature2 on feature1 = linear combined history [OK]

Hint: Rebase feature2 on feature1 for clean linear history [OK]

Common Mistakes:

• Thinking rebasing deletes branches
• Confusing rebase with merge into main
• Ignoring the order of branches in rebase