Git Commit Amend: Updating the Latest Commit and Fixing Messages

It happens to every engineer: you hit Enter on git commit -m "feat: implement payment gateway", and three seconds later you realize you forgot to stage config.stripe.js, or you made a glaring spelling mistake in your commit title. The --amend flag is Git's built-in eraser for the latest commit.

Scenario 1: Fixing a Typo in the Last Commit Message

If you don't need to change any files and only want to correct the commit message, run:

# Open your default editor to rewrite the message:
$ git commit --amend

# Or supply the corrected message directly in terminal:
$ git commit --amend -m "feat(payment): implement Stripe payment gateway"

Scenario 2: Adding Forgotten Files to the Last Commit

If you forgot to include a file (or made a quick two-line bugfix that belongs in the previous commit):

1. Make your edits or create your missing files.
2. Stage the files using git add.
3. Run git commit --amend --no-edit.

# Stage the forgotten file:
$ git add src/config/stripe.js

# Merge it into the last commit without prompting for a new message:
$ git commit --amend --no-edit

The --no-edit flag tells Git to keep the existing commit message while absorbing the newly staged changes directly into the previous commit.

What Actually Happens Under the Hood?

It is vital to understand that Git does NOT physically edit the existing commit object. Commits in Git are immutable. When you run --amend, Git creates a brand-new commit object with a new SHA-1 hash and points the branch reference to it, abandoning the old commit.