git fixup — Amending Previous Commits

What is a Fixup?

A fixup commit is a special type of squash commit that targets a specific earlier commit for amendment. When you run git rebase --autosquash, Git automatically:

1. Moves the fixup commit directly below its target
2. Squashes it into the target commit
3. Discards the fixup commit's message (unlike squash, which keeps it)

This is the cleanest workflow for correcting earlier commits in a feature branch without disturbing everything else.

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The Workflow

Step 1 — Find the SHA of the commit you want to fix

git log --oneline
# 1a4b5c6 feat(transactions): add controller endpoint
# 9f3e2d1 feat(transactions): add service logic         ← I need to fix this one
# 7d1e4f0 feat(transactions): add repository
# a3f9bc2 feat(transactions): add domain model

Step 2 — Make your fix and create a fixup commit

# Edit the file
vim src/main/java/com/example/TransactionService.java

# Stage it
git add src/main/java/com/example/TransactionService.java

# Create a fixup commit targeting the SHA of the commit to fix
git commit --fixup 9f3e2d1
# Creates a commit with the message: "fixup! feat(transactions): add service logic"

Git automatically prefixes the message with fixup! followed by the target commit's subject. This is the token --autosquash recognises.

git log --oneline
# b7e2a1f fixup! feat(transactions): add service logic   ← new fixup commit
# 1a4b5c6 feat(transactions): add controller endpoint
# 9f3e2d1 feat(transactions): add service logic
# 7d1e4f0 feat(transactions): add repository
# a3f9bc2 feat(transactions): add domain model

You can continue working and create as many fixup commits as needed.

Step 3 — Clean up with autosquash rebase

When ready to clean up (before opening a PR):

git rebase -i --autosquash origin/main

Git automatically rearranges the todo list — moving fixup commits below their targets and marking them as fixup:

pick a3f9bc2 feat(transactions): add domain model
pick 7d1e4f0 feat(transactions): add repository
pick 9f3e2d1 feat(transactions): add service logic
fixup b7e2a1f fixup! feat(transactions): add service logic   ← auto-arranged
pick 1a4b5c6 feat(transactions): add controller endpoint

Save and close. Git squashes b7e2a1f into 9f3e2d1 and discards the fixup message. The result is clean history as if the original commit was always correct.

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Make Autosquash the Default

git config --global rebase.autoSquash true
# Now git rebase -i always enables autosquash

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--fixup vs --squash

	--fixup	--squash
Message	Discarded (prefixed fixup! )	Kept (prefixed squash! )
Good for	Silent corrections — typos, missed null checks, formatting	Meaningful additions worth documenting

# Fixup (silent correction — message discarded)
git commit --fixup 9f3e2d1

# Squash (meaningful addition — message included in final commit)
git commit --squash 9f3e2d1

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Fixup with Amend (--fixup=amend:)

Git 2.32+ supports fixup with message amendment in one step:

# Fix the changes AND reword the target commit's message
git commit --fixup=amend:9f3e2d1

This creates a amend! prefixed commit that, during autosquash rebase, will both apply the changes AND open the editor to let you reword the target commit's message.

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Full Example in a Real Workflow

# Working on a feature branch
git switch -c feature/JIRA-123

# Make commits as you develop
git commit -m "feat(transactions): add domain model"
git commit -m "feat(transactions): add repository"
git commit -m "feat(transactions): add service"

# Reviewer asks you to fix a validation edge case in the service
vim src/main/java/com/example/TransactionService.java
git add .
git commit --fixup HEAD~0   # fixup the most recent commit
# or target a specific earlier commit:
git commit --fixup abc1234

# Add another fix from a review comment
vim src/main/java/com/example/dto/TransactionDto.java
git add .
git commit --fixup abc1234  # same target — multiple fixups are fine

# Before merging, clean up the entire branch
git rebase -i --autosquash origin/main

# Force push the cleaned branch
git push --force-with-lease origin feature/JIRA-123

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Set Up a Shell Alias

Speed up the fixup workflow with a shell alias:

# .bashrc / .zshrc
alias gfix='git commit --fixup'

# Usage:
gfix 9f3e2d1

Combined with git config --global rebase.autoSquash true, this becomes the fastest way to maintain clean branch history.