Interactive rebase (git rebase -i) - Mini Project: Build & Apply

Interactive Rebase with git rebase -i

📖 Scenario: You are working on a small project with a few commits. You want to clean up your commit history before sharing your work with your team. This means combining some commits and editing commit messages to make the history clearer.

🎯 Goal: Learn how to use git rebase -i to interactively edit, squash, and reorder commits in your local git repository.

📋 What You'll Learn

Have git installed and a local git repository initialized

Have at least 3 commits in your current branch

Use git rebase -i to modify commit history

Understand basic git commands like git log and git commit

💡 Why This Matters

🌍 Real World

Cleaning up commit history before sharing code helps keep project history clear and understandable for everyone.

💼 Career

Using interactive rebase is a common skill for developers and DevOps engineers to maintain clean and professional git histories.

1

Create initial commits

Create three commits in your git repository with these exact commit messages in order: "Add README", "Add LICENSE", and "Update README". Use git commit with the -m option to set the messages.

Git

# Create three commits with messages "Add README", "Add LICENSE", and "Update README"
# Your git commands here

Hint

Use git commit --allow-empty -m "message" to create commits without changing files.

2

Start interactive rebase

Run git rebase -i HEAD~3 to start an interactive rebase for the last three commits.

Git

git commit --allow-empty -m "Add README"
git commit --allow-empty -m "Add LICENSE"
git commit --allow-empty -m "Update README"
# Run interactive rebase for last 3 commits
# Your command here

Hint

The command git rebase -i HEAD~3 opens the last 3 commits for editing.

3

Edit the rebase todo list

In the opened editor, change the second commit's action from pick to squash to combine it with the first commit. Leave the others as pick. Save and close the editor to continue.

Git

git commit --allow-empty -m "Add README"
git commit --allow-empty -m "Add LICENSE"
git commit --allow-empty -m "Update README"
git rebase -i HEAD~3
# Change 'pick' to 'squash' for the second commit in the editor
# Save and close the editor

Hint

Change only the second commit's action from pick to squash in the editor that opens after running git rebase -i.

4

View the updated commit history

Run git log --oneline -3 to display the last three commits and verify that the second commit was squashed into the first.

Git

git commit --allow-empty -m "Add README"
git commit --allow-empty -m "Add LICENSE"
git commit --allow-empty -m "Update README"
git rebase -i HEAD~3
# In editor:
# pick  Add README
# squash  Add LICENSE
# pick  Update README
# Save and close editor
# Run git log to check commits
# Your command here

Hint

The output of git log --oneline -3 should show two commits with messages including "Add README" and "Update README" after squashing.

Practice

1. What is the main purpose of using git rebase -i (interactive rebase)?

easy

A. To reorder, edit, or combine recent commits before sharing

B. To create a new branch from the current commit

C. To permanently delete the entire commit history

D. To push commits directly to the remote repository

Solution

1. Step 1: Understand the purpose of interactive rebase

   Interactive rebase allows you to change the order, combine, edit, or remove recent commits.

2. Step 2: Compare with other git commands

   Creating branches, deleting history, or pushing commits are different git operations.

3. Final Answer:

   To reorder, edit, or combine recent commits before sharing -> Option A

4. Quick Check:

   Interactive rebase = reorder/edit commits [OK]

Hint: Interactive rebase = rewrite recent commits easily [OK]

Common Mistakes:

• Confusing rebase with branch creation
• Thinking it deletes all history
• Assuming it pushes commits automatically

2. Which of the following is the correct command to start an interactive rebase for the last 3 commits?

easy

A. git rebase -i HEAD^^3

B. git rebase -i HEAD~3

C. git rebase -i HEAD~

D. git rebase -i HEAD^3

Solution

1. Step 1: Recall the syntax for interactive rebase

   The correct syntax uses HEAD~N to specify the last N commits, so HEAD~3 means last 3 commits.

2. Step 2: Check the options

   HEAD^3 and HEAD^^3 are invalid for this purpose; HEAD~ alone is incomplete.

3. Final Answer:

   git rebase -i HEAD~3 -> Option B

4. Quick Check:

   HEAD~3 selects last 3 commits [OK]

Hint: Use HEAD~N to select last N commits for rebase [OK]

Common Mistakes:

• Using HEAD^3 instead of HEAD~3
• Omitting the number after ~
• Using double carets ^^ incorrectly

3. Given the following interactive rebase todo list:

pick a1b2c3 Commit A
pick d4e5f6 Commit B
pick 789abc Commit C

If you change it to:

pick d4e5f6 Commit B
squash 789abc Commit C
pick a1b2c3 Commit A

What will happen after completing the rebase?

medium

A. Only Commit C will be applied, others dropped

B. Commits A and B will be combined, Commit C will be last

C. The rebase will fail due to invalid order

D. Commits B and C will be combined, and Commit A will be last

Solution

1. Step 1: Understand 'pick' and 'squash' in rebase

   'pick' applies a commit as is; 'squash' combines the commit with the previous one.

2. Step 2: Analyze the new order

   Commit B is picked first, Commit C is squashed into B, Commit A is picked last.

3. Final Answer:

   Commits B and C will be combined, and Commit A will be last -> Option D

4. Quick Check:

   squash merges commits; order changed [OK]

Hint: Squash merges commit into previous one in order [OK]

Common Mistakes:

• Thinking squash drops commits
• Assuming order stays same after rebase
• Confusing squash with fixup

4. You run git rebase -i HEAD~2 and change the second commit's action from pick to edit. After saving, what should you do next to modify that commit?

medium

A. Make changes, then run git commit --amend and git rebase --continue

B. Run git push immediately to update remote

C. Abort the rebase with git rebase --abort

D. Run git reset --hard HEAD~1 to undo the commit

Solution

1. Step 1: Understand 'edit' in interactive rebase

   When a commit is marked 'edit', rebase pauses to let you change it.

2. Step 2: Modify commit and continue rebase

   You make changes, amend the commit with git commit --amend, then continue with git rebase --continue.

3. Final Answer:

   Make changes, then run git commit --amend and git rebase --continue -> Option A

4. Quick Check:

   Edit = amend commit + continue rebase [OK]

Hint: Edit commit: amend changes, then continue rebase [OK]

Common Mistakes:

• Pushing before finishing rebase
• Aborting instead of continuing
• Resetting commits incorrectly

5. You want to clean up your last 4 commits by combining the second and third commits into one, and also reorder commits so the last commit becomes the first. Which interactive rebase todo list correctly achieves this?

pick 111aaa Commit 1
pick 222bbb Commit 2
pick 333ccc Commit 3
pick 444ddd Commit 4

hard

A. pick 444ddd Commit 4
squash 222bbb Commit 2
pick 333ccc Commit 3
pick 111aaa Commit 1

B. pick 444ddd Commit 4
pick 111aaa Commit 1
squash 222bbb Commit 2
pick 333ccc Commit 3

C. pick 444ddd Commit 4
pick 111aaa Commit 1
pick 222bbb Commit 2
squash 333ccc Commit 3

D. pick 111aaa Commit 1
pick 333ccc Commit 3
squash 222bbb Commit 2
pick 444ddd Commit 4

Solution

1. Step 1: Reorder commits to put last commit first

   Commit 4 (444ddd) should be first in the list to reorder it first.

2. Step 2: Combine second and third commits

   To combine commits 2 and 3, use 'pick' on commit 2 and 'squash' on commit 3 immediately after.

3. Step 3: Verify the todo list

   pick 444ddd Commit 4
   pick 111aaa Commit 1
   pick 222bbb Commit 2
   squash 333ccc Commit 3

   places commit 4 first, then commit 1, then picks commit 2 and squashes commit 3, matching requirements.

4. Final Answer:

   pick 444ddd Commit 4
   pick 111aaa Commit 1
   pick 222bbb Commit 2
   squash 333ccc Commit 3

   -> Option C

5. Quick Check:

   Reorder + squash =

   pick 444ddd Commit 4
   pick 111aaa Commit 1
   pick 222bbb Commit 2
   squash 333ccc Commit 3

   [OK]

Hint: Put last commit first, squash 3rd into 2nd commit [OK]

Common Mistakes:

• Squashing commits in wrong order
• Not moving last commit to first position
• Using squash on wrong commits