dtsong/Git Squash

Scope Constraints

• Destructive write operation — rewrites commit history by combining multiple commits via soft reset
• Operates on local commits only — does not push to remote
• Requires --force-with-lease push after squashing already-pushed commits
• Does not modify files — only restructures commit history

Input Sanitization

• Commit count: must be a positive integer greater than 1, or --since <branch>, or --all. Reject zero, negative numbers, non-numeric input, and shell metacharacters.
• Branch name (--since): only alphanumeric characters, hyphens, underscores, and forward slashes. Reject spaces, .., or null bytes.

/git-squash - Squash Commits

Combine multiple commits into fewer, cleaner commits non-interactively.

Usage

/git-squash 3               # Squash last 3 commits into 1
/git-squash --since main    # Squash all commits since main
/git-squash --all           # Squash all commits on branch into 1
/git-squash --preview       # Show what would be squashed

When to Use

• Before PR: Clean up WIP commits into logical units
• After review: Squash fixup commits
• Messy history: Combine related small commits
• Before merge: Create clean, meaningful commits

Workflow

Step 1: Determine Commits to Squash

# Last N commits
SQUASH_COUNT=3

# Or commits since branching from main
SQUASH_COUNT=$(git rev-list --count main..HEAD)

# Show commits that will be squashed
echo "Commits to squash:"
git log --oneline -n "$SQUASH_COUNT"

Step 2: Pre-flight Checks

# Check for uncommitted changes
if ! git diff --quiet || ! git diff --cached --quiet; then
    echo "Commit or stash your changes first."
    exit 1
fi

# Ensure we have commits to squash
if [ "$SQUASH_COUNT" -lt 2 ]; then
    echo "Need at least 2 commits to squash."
    exit 1
fi

Step 3: Create Squash Commit Message

# Gather all commit messages
MESSAGES=$(git log --format="%s" -n "$SQUASH_COUNT" | tac)

# Generate combined message
BRANCH=$(git branch --show-current)
echo "Squashed commits from $BRANCH:"
echo ""
echo "$MESSAGES"

Step 4: Execute Squash (Non-Interactive)

# Soft reset to keep changes staged
git reset --soft HEAD~"$SQUASH_COUNT"

# Create new commit with combined message
git commit -m "Combined message here"

Step 5: Report Result

Show the squash result and next steps.

Output Format

Preview Mode

Would squash 5 commits:

  abc1234 WIP: starting feature
  def5678 More work on feature
  ghi9012 Fix typo
  jkl3456 Actually fix the bug
  mno7890 Final touches

Combined changes:
  4 files changed, 123 insertions(+), 45 deletions(-)

  src/components/Feature.tsx
  src/hooks/useFeature.ts
  src/styles/feature.css
  tests/feature.test.ts

Run without --preview to execute.

Successful Squash

Squashed 5 commits into 1:

Before:
  abc1234 WIP: starting feature
  def5678 More work on feature
  ghi9012 Fix typo
  jkl3456 Actually fix the bug
  mno7890 Final touches

After:
  xyz7890 Add feature component with styles and tests

Files in squashed commit:
  src/components/Feature.tsx
  src/hooks/useFeature.ts
  src/styles/feature.css
  tests/feature.test.ts

Note: History was rewritten. If already pushed:
  git push --force-with-lease

Squash All Since Main

Squashing all commits since main (7 commits)...

Before:
  (7 commits with various WIP messages)

After:
  feat: Add complete dark mode implementation

  - Theme toggle component
  - System theme detection
  - Persistent preference storage
  - Updated color palette

Ready for PR! Run:
  /git-push --force-with-lease
  /commit-push-pr

Commit Message Strategies

Option 1: Single Summary

feat: Add user authentication

Implements login, logout, and session management.

Option 2: Bullet Points (for larger squashes)

feat: Add user authentication

- Add login form component
- Implement session management
- Add logout functionality
- Add remember me option
- Add password reset flow

Option 3: Preserve Original Messages

feat: Add user authentication

Squashed commits:
- Add login form component
- Wire up authentication API
- Add session storage
- Fix validation bugs
- Add tests

Interactive Alternative

For more control, use interactive rebase:

# Interactive rebase for last 5 commits
git rebase -i HEAD~5

# In editor, change 'pick' to 'squash' (or 's') for commits to combine
# Then edit the combined commit message

Note: Claude cannot run interactive commands, but can guide you through them.

Safety Notes

1. Only squash unpushed commits: Or commits on your personal branch
2. Never squash shared history: Others may have based work on it
3. Force push needed: After squashing pushed commits
4. Backup first: If unsure, create a backup branch

# Create backup before squashing
git branch backup-before-squash

Integration

• Use before /git-push to clean up history
• Use before /commit-push-pr for clean PRs
• Use /git-push --force-with-lease after squashing pushed commits
• Consider PR squash-merge instead for simple cases