Editing commit messages with rebase in Git - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of interactive rebase command

You run the command git rebase -i HEAD~3 to edit the last 3 commits. What will Git open for you?

A A merge conflict resolution tool.

B A list of all branches in the repository.

C A text editor showing the last 3 commits with options to pick, squash, or edit each commit message.

D The commit history graph in the terminal.

💡 Hint

Think about what interactive rebase is used for.

The command git rebase -i HEAD~3 opens an editor with the last 3 commits listed. You can choose to edit commit messages, reorder commits, squash commits, or drop commits.

🔀 Workflow

intermediate

Steps to change a commit message in the middle of history

You want to change the commit message of the second last commit in your branch. Which sequence of commands correctly achieves this?

A git rebase -i HEAD~2, then change 'pick' to 'reword' for the second commit, save and exit, then edit the message when prompted.

B git commit --amend on the second last commit directly.

C git reset --soft HEAD~2, then git commit with new message.

D git checkout second_last_commit, then git commit --amend.

💡 Hint

Amending only works on the latest commit.

To change a commit message in the middle of history, you use interactive rebase and mark the commit with 'reword' to edit its message.

❓ Troubleshoot

advanced

Error during rebase when editing commit message

You run git rebase -i HEAD~4 and change a commit message, but Git stops with the error: error: could not apply . What is the most likely cause?

A Your Git version does not support interactive rebase.

B There is a conflict between the commit being rebased and later commits that must be resolved manually.

C The commit message contains invalid characters.

D You forgot to save the commit message after editing.

💡 Hint

Think about what happens when commits change history.

During rebase, if changes conflict with later commits, Git pauses and asks you to resolve conflicts before continuing.

🧠 Conceptual

advanced

Effect of rebase on commit hashes after editing messages

After editing a commit message using interactive rebase, what happens to the commit hash of that commit and its descendants?

A The commit hash of the edited commit and all its descendants change because commit hashes depend on commit content.

B Only the edited commit's hash changes; descendants keep their original hashes.

C None of the commit hashes change because messages do not affect hashes.

D Only the descendants' hashes change; the edited commit's hash stays the same.

💡 Hint

Commit hashes are based on the commit content including the message.

Changing a commit message changes the commit content, so its hash changes. This causes all descendant commits to get new hashes as well.

✅ Best Practice

expert

Best practice when rewriting commit messages on a shared branch

You need to rewrite commit messages on a branch that others have already pulled. What is the best practice to avoid problems?

A Rebase and force push immediately without informing anyone.

B Avoid rewriting history; instead, add new commits that fix messages.

C Delete the remote branch and push a new branch with the rewritten history.

D Communicate with your team, perform the rebase locally, then force push the branch with <code>git push --force-with-lease</code>.

💡 Hint

Think about collaboration and safety when rewriting history.

Rewriting history on shared branches can cause problems. Informing the team and using --force-with-lease helps avoid overwriting others' work.

Practice

1. What does the command git rebase -i HEAD~3 allow you to do?

easy

A. Delete the last 3 commits permanently

B. View the commit history without changes

C. Create 3 new commits automatically

D. Interactively edit the last 3 commits, including their messages

Solution

1. Step 1: Understand the command purpose

   git rebase -i HEAD~3 opens an interactive editor for the last 3 commits.

2. Step 2: Recognize the interactive editing feature

   It allows changing commit messages, reordering, or squashing commits.

3. Final Answer:

   Interactively edit the last 3 commits, including their messages -> Option D

4. Quick Check:

   Interactive rebase edits commits [OK]

Hint: Use -i with HEAD~N to edit last N commits [OK]

Common Mistakes:

• Thinking it deletes commits
• Assuming it creates new commits
• Confusing it with git log

2. Which line correctly changes a commit action to edit its message during an interactive rebase?

easy

A. reword abc123 Update README with new info

B. pick abc123 Fix typo in README

C. edit abc123 Add new feature

D. delete abc123 Remove unused file

Solution

1. Step 1: Identify the correct keyword for editing messages

   In interactive rebase, reword lets you change the commit message only.

2. Step 2: Compare options

   edit pauses for full commit changes, pick keeps commit as is, delete is invalid here.

3. Final Answer:

   reword abc123 Update README with new info -> Option A

4. Quick Check:

   Use 'reword' to edit message only [OK]

Hint: Change 'pick' to 'reword' to edit commit messages [OK]

Common Mistakes:

• Using 'edit' when only message change is needed
• Leaving 'pick' unchanged
• Using invalid 'delete' keyword

3. After running git rebase -i HEAD~2 and changing the first commit's action from pick to reword, what happens next?

medium

A. Git deletes the first commit

B. Git opens an editor to change the first commit message, then continues rebase

C. Git aborts the rebase immediately

D. Git merges the two commits automatically

Solution

1. Step 1: Understand 'reword' effect during rebase

   Changing 'pick' to 'reword' tells Git to pause and open the commit message editor for that commit.

2. Step 2: Follow rebase process

   After editing the message, Git continues applying remaining commits automatically.

3. Final Answer:

   Git opens an editor to change the first commit message, then continues rebase -> Option B

4. Quick Check:

   'reword' opens message editor [OK]

Hint: Reword pauses to edit message, then continues [OK]

Common Mistakes:

• Thinking rebase aborts on reword
• Assuming commits get deleted
• Expecting automatic merge without editing

4. You ran git rebase -i HEAD~2 and changed 'pick' to 'reword' for the second commit, but after saving, Git shows an error: error: could not apply abc123. What is the likely cause?

medium

A. You used 'reword' instead of 'edit'

B. You forgot to save the commit message editor

C. There is a conflict applying the second commit during rebase

D. The commit hash is invalid

Solution

1. Step 1: Understand the error message

   error: could not apply abc123 means Git failed to apply that commit, usually due to conflicts.

2. Step 2: Relate to rebase process

   During rebase, conflicts can happen if changes overlap; you must resolve them manually.

3. Final Answer:

   There is a conflict applying the second commit during rebase -> Option C

4. Quick Check:

   Apply error = conflict during rebase [OK]

Hint: Apply errors usually mean conflicts to resolve [OK]

Common Mistakes:

• Assuming 'reword' causes error by itself
• Ignoring conflict resolution step
• Thinking commit hash is wrong

5. You want to edit the commit messages of the last 4 commits but keep the commit content unchanged. Which sequence of commands and actions is correct?

hard

A. Run git rebase -i HEAD~4, change all 'pick' to 'reword', save, then edit each message when prompted

B. Run git commit --amend four times in a row

C. Run git reset --soft HEAD~4 and recommit with new messages

D. Run git rebase -i HEAD~4, change 'pick' to 'edit', then change messages and contents

Solution

1. Step 1: Choose the right rebase command

   git rebase -i HEAD~4 opens interactive rebase for last 4 commits.

2. Step 2: Use 'reword' to edit messages only

   Changing 'pick' to 'reword' lets you edit commit messages without changing content.

3. Step 3: Save and edit messages when prompted

   Git opens editor for each commit message in turn; you update and save them.

4. Final Answer:

   Run git rebase -i HEAD~4, change all 'pick' to 'reword', save, then edit each message when prompted -> Option A

5. Quick Check:

   Use 'reword' in interactive rebase for message edits only [OK]

Hint: Use 'reword' for messages, 'edit' for content changes [OK]

Common Mistakes:

• Using commit --amend repeatedly instead of rebase
• Resetting and recommitting loses history
• Using 'edit' when only message change needed