Amending the last commit in Git - Commands & Configuration

Introduction

Sometimes you make a commit and realize you forgot to add a file or want to change the commit message. Amending the last commit lets you fix that without making a new commit.

When you forgot to include a file in your last commit and want to add it.

When you want to correct a typo or improve the message of your last commit.

When you want to combine small changes into the previous commit to keep history clean.

When you accidentally committed with the wrong message and want to fix it before pushing.

When you want to update the last commit with new changes before sharing your work.

Commands

Add the file 'example.txt' to the staging area so it will be included in the next commit.

Terminal

git add example.txt

Expected Output

No output (command runs silently)

Replace the last commit with a new one that includes the staged changes and updates the commit message to 'Fix typo in example.txt'.

Terminal

git commit --amend -m "Fix typo in example.txt"

Expected Output

[master 1a2b3c4] Fix typo in example.txt

 Date: Thu Jun 1 12:00:00 2024 +0000

 1 file changed, 1 insertion(+), 1 deletion(-)

→

--amend - Replace the last commit with the new staged changes.

→

-m - Provide a new commit message inline.

Show the latest commit in a short format to verify the amended commit message and hash.

Terminal

git log -1 --oneline

Expected Output

1a2b3c4 Fix typo in example.txt

→

-1 - Show only the most recent commit.

→

--oneline - Display commit in a concise single line.

Key Concept

If you remember nothing else from this pattern, remember: git commit --amend lets you fix your last commit by adding changes or updating its message before pushing.

Common Mistakes

Running git commit --amend without staging any changes.

This only changes the commit message but does not add any new files or changes.

Stage the files you want to add with git add before running git commit --amend.

Amending a commit after it has been pushed to a shared repository.

This rewrites history and can cause problems for others who already pulled the original commit.

Only amend commits that have not been pushed yet, or coordinate with your team if you must rewrite history.

Forgetting to update the commit message when amending changes.

The old message remains, which might not reflect the new changes accurately.

Use the -m flag to provide a clear, updated commit message during amend.

Summary

Use git add to stage any new or changed files you want to include in the last commit.

Run git commit --amend -m "new message" to replace the last commit with your staged changes and update the message.

Verify the amended commit with git log -1 --oneline to ensure your changes and message are correct.

Practice

1. What does the git commit --amend command do?

easy

A. It modifies the last commit by changing its message or content.

B. It deletes the last commit permanently.

C. It creates a new commit without changing previous commits.

D. It resets the repository to the initial commit.

Solution

1. Step 1: Understand the purpose of git commit --amend

   This command is used to change the last commit, either by editing its message or adding new changes.

2. Step 2: Compare with other options

   Deleting commits or resetting the repository are different commands like git reset. Creating a new commit does not amend the last one.

3. Final Answer:

   It modifies the last commit by changing its message or content. -> Option A

4. Quick Check:

   Amend last commit = modify last commit [OK]

Hint: Amend changes last commit, not create or delete [OK]

Common Mistakes:

• Thinking it deletes the last commit
• Confusing amend with creating a new commit
• Assuming it resets the whole repo

2. Which of the following is the correct syntax to amend the last commit message in Git?

easy

A. git commit -amend "New message"

B. git amend commit -m "New message"

C. git commit --amend -m "New message"

D. git commit --edit-message "New message"

Solution

1. Step 1: Recall the correct syntax for amending commit message

   The correct command is git commit --amend -m "New message" to directly change the last commit message.

2. Step 2: Identify incorrect syntax

   Options B, C, and D use invalid flags or wrong order, which Git does not recognize.

3. Final Answer:

   git commit --amend -m "New message" -> Option C

4. Quick Check:

   Correct amend syntax = git commit --amend -m [OK]

Hint: Use --amend before -m to change message [OK]

Common Mistakes:

• Swapping order of flags
• Using non-existent flags like --edit-message
• Typing 'amend' as a separate command

3. Given the following commands executed in order:

echo "Hello" > file.txt
 git add file.txt
 git commit -m "Add file"
 echo "World" >> file.txt
 git add file.txt
 git commit --amend -m "Add file with content update"

What will git log -1 --pretty=%B output?

medium

A. Add file

B. Add file with content update

C. Add file
Add file with content update

D. No commit message

Solution

1. Step 1: Understand the commit history after commands

   First commit message is "Add file". Then file.txt is updated and staged. The git commit --amend replaces the last commit message with "Add file with content update".

2. Step 2: Check the latest commit message output

   The git log -1 --pretty=%B shows the last commit message, which is now "Add file with content update" after amend.

3. Final Answer:

   Add file with content update -> Option B

4. Quick Check:

   Amended commit message = updated message [OK]

Hint: Amend replaces last commit message and content [OK]

Common Mistakes:

• Thinking amend adds a new commit instead of replacing
• Expecting both messages to appear
• Assuming commit message stays unchanged

4. You ran git commit --amend but accidentally removed some changes from the last commit. How can you fix this?

medium

A. Delete the repository and clone again.

B. Run git commit --amend again without changes.

C. Use git push --force to overwrite remote.

D. Use git reflog to find the previous commit and reset to it.

Solution

1. Step 1: Understand the problem with amend

   Amending rewrites the last commit, so if changes were lost, the previous commit state is still in Git history.

2. Step 2: Use git reflog to recover

   git reflog shows recent commit states. You can find the commit before amend and reset to it to restore lost changes.

3. Final Answer:

   Use git reflog to find the previous commit and reset to it. -> Option D

4. Quick Check:

   Recover lost commit with reflog [OK]

Hint: Use reflog to recover lost commits after amend [OK]

Common Mistakes:

• Trying to fix by amending again without changes
• Deleting repo instead of recovering
• Forcing push without fixing local history

5. You committed a file with a typo in the message and forgot to add a new file. Which sequence correctly fixes both issues using amend?

hard

A. Add the new file, then run git commit --amend -m "Corrected message"

B. Run git commit --amend -m "Corrected message" first, then add the new file

C. Delete the last commit, add the new file, then commit again

D. Push the commit, then fix the message and add file in a new commit

Solution

1. Step 1: Stage the new file before amending

   To include the new file in the last commit, you must add it first with git add.

2. Step 2: Amend the commit with the corrected message

   Run git commit --amend -m "Corrected message" to update the commit message and include the staged new file.

3. Final Answer:

   Add the new file, then run git commit --amend -m "Corrected message" -> Option A

4. Quick Check:

   Stage files before amend to include them [OK]

Hint: Add files first, then amend commit message [OK]

Common Mistakes:

• Amending before adding new files
• Deleting commits unnecessarily
• Pushing before fixing local commit