Git rebase

Git Rebase — Craft a Clean History

Core Mental Model

Before rebase (merge commits clutter history):
A───M───A'───M'───A''     (M = merge commits)

After rebase (linear, readable):
A───A'───A''───A'''       (no merge commits, one clean line)

Golden rule: Never rebase commits that have been pushed to a shared branch.

Interactive Rebase (git rebase -i)

How it works

# Rebase last N commits interactively
git rebase -i HEAD~3

# Opens editor with:
pick abc1234 Add user authentication
pick def5678 Fix typo in auth
pick ghi9012 Add password validation

# Editor commands (change "pick" to these):
pick   → keep commit as-is
reword → keep commit, change message
edit   → stop here, amend/rebase manually
squash → combine with previous commit
fixup  → like squash, discard this commit's message
drop   → remove commit
reorder→ move lines up/down

Example: Clean up a messy branch before PR

git rebase -i HEAD~5

pick  a1b2c3d WIP: started auth
pick  e4f5g6h WIP: auth working
pick  i7j8k9l Fixed bug in auth (oops, went in wrong commit)
pick  m1n2o3p Add password validation
pick  q4r5s6t Final polish

# Change to:
pick  a1b2c3d WIP: started auth
f     i7j8k9l Fix bug in auth (squash into previous)
f     e4f5g6h WIP: auth working (squash into first)
pick  m1n2o3p Add password validation
r     q4r5s6t Final polish: add complete auth flow

Result: 3 clean commits instead of 5 messy ones.

Common Operations

1. Squash consecutive commits

# Squash last 3 commits into one
git rebase -i HEAD~3
# Mark 2nd and 3rd as "squash" or "fixup"

2. Split a commit into multiple

git rebase -i HEAD~1
# Mark the commit as "edit"

# When rebase stops at that commit:
git reset HEAD~1
# Now commit pieces separately:
git add src/auth.go && git commit -m "Add auth package"
git add src/auth_test.go && git commit -m "Add auth tests"
git add src/middleware.go && git commit -m "Add auth middleware"

# Continue rebase:
git rebase --continue

3. Reorder commits

git rebase -i HEAD~4
# Move commit lines to reorder
# e.g., move "Add tests" before "Add feature"

4. Edit an old commit message

git rebase -i HEAD~5
# Change "pick" to "reword" for the relevant commit

5. Drop a commit entirely

git rebase -i HEAD~5
# Change "pick" to "drop" for the commit to remove

6. Apply a commit from one branch onto another (rebase vs cherry-pick)

# Cherry-pick: apply specific commits from anywhere
git cherry-pick abc1234

# Rebase: move entire branch on top of another
git checkout feature
git rebase main
# Now feature/ is on top of main/

Conflict Resolution During Rebase

# When conflicts occur during rebase:
git status
# → both modified: src/auth.go

# Fix the conflict manually:
vim src/auth.go  # resolve <<<<<< and >>>>>> markers

git add src/auth.go
git rebase --continue

# If you want to abandon the rebase entirely:
git rebase --abort

Rebasing with autosquash (auto-group fixup commits)

#标记fixup的提交:
git commit --fixup abc1234

#稍后自动squash:
git rebase -i --autosquash main

Branching Strategies Compared

Git Flow (Heavy)

main ──────────────────────────── (production releases)
  └ develop ──────────────────── (integration)
       ├─ feature/user-auth ──── (rebase onto develop, squash)
       ├─ feature/billing ──────
       └─ release/1.4 ───────── (rebase, test, merge)

Trunk-Based Development (Light)

main ──●───●───●───●───●──●─── (everyone commits to main)
          └─ feature/auth
          └─ feature/billing
          # Short-lived branches (< 1 day), rebase onto main frequently

Rebase Workflow

# Daily workflow (trunk-based):
git checkout main && git pull --rebase
git checkout -b feature/auth

# Make commits (clean, atomic):
git add src/auth.go && git commit -m "Add JWT token generation"
git add src/auth_test.go && git commit -m "Test JWT token generation"

# Before PR:
git fetch origin
git rebase -i origin/main
# Squash, reorder, clean up

# Push (with force to update PR):
git push --force-with-lease  # --force-with-lease is safer than --force

Reflog — Your Safety Net

# See everything you've done (even after rebase --abort):
git reflog
# 3a2b1c0 HEAD@{0}: rebase (finish): returning to refs/heads/feature/auth
# 9x8y7z6 HEAD@{1}: rebase (interactive): editing
# ...

# Restore to before a bad rebase:
git checkout feature/auth
git reset --hard HEAD@{1}  # or use the specific reflog entry

# Or recover a "lost" commit:
git reflog | grep "abc123"  # find where the commit was
git cherry-pick abc1234      # apply it back

Advanced: filter-repo

For mass history rewriting (remove secrets, rename files across history):

# Install
pip install git-filter-repo

# Remove a file from entire history (e.g., accidentally committed secrets)
git filter-repo --path secret.txt --invert-paths --force

# Rename file throughout history
git filter-repo --path-rename old_name/:new_name/ --force

# Change committer emails across entire history
git filter-repo --mailmap author-script  # see git-shortlog(1)

⚠️ filter-repo rewrites history permanently. Always work on a fresh clone.

Rebase vs Merge — When to Use Each

Situation	Use
Cleaning up local commits before PR	rebase -i
Bringing feature up to date with main	rebase
Integrating a finished feature branch	merge
Collaborative/shared branches	merge (never rebase)
Fast-forward only (clean history)	git merge --ff-only
Public/shared branch has bad commits	git revert (never rebase)
Long-running feature branch	Periodic rebase onto main

Pre-PR Checklist

Before pushing and opening a PR:

□ Rebased onto latest target branch
□ Commits are atomic (one logical change per commit)
□ No "WIP" or "fix" commits (squash them)
□ Commit messages follow convention: type(scope): description
□ Force-with-lease used (not force push)
□ Tests pass locally
□ History is readable as a story

Commit Message Convention

type(scope): short description (50 chars max)

Optional longer description (wrap at 72 chars)

Footer: references/issues

Types:
  feat:     new feature
  fix:      bug fix
  refactor: code change that neither fixes a bug nor adds a feature
  test:     adding or correcting tests
  docs:     documentation only
  chore:    maintenance tasks (deps, config)
  perf:     performance improvement

Examples:
  feat(auth): add JWT token generation and validation
  fix(checkout): prevent negative quantity in cart
  refactor(orders): extract payment service from order controller
  test(api): add property-based tests for order serialization

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When to Trigger This Skill

• Cleaning up commit history before PR
• Interactive rebase, squash, reorder, or split commits
• Rebase conflict resolution
• Git history archaeology (who wrote this, why)
• git reflog to recover from mistakes
• filter-repo for mass history rewriting
• Git workflow advice (rebase vs merge)
• Fixing commit messages after push

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Last updated: 2026-03-28