git-workflow

name	git-workflow
description	Gitワークフロー、ブランチ戦略、コミットメッセージ規約、およびプルリクエストプロセス。
origin	ECC

Git Workflow Patterns

Best practices for Git version control, branching strategies, and collaborative development.

When to Activate

• Setting up Git workflow for a new project
• Deciding on branching strategy (GitFlow, trunk-based, GitHub flow)
• Writing commit messages and PR descriptions
• Resolving merge conflicts
• Managing releases and version tags
• Onboarding new team members to Git practices

Branching Strategies

GitHub Flow (Simple, Recommended for Most)

Best for continuous deployment and small-to-medium teams.

main (protected, always deployable)
  │
  ├── feature/user-auth      → PR → merge to main
  ├── feature/payment-flow   → PR → merge to main
  └── fix/login-bug          → PR → merge to main

Rules:

• main is always deployable
• Create feature branches from main
• Open Pull Request when ready for review
• After approval and CI passes, merge to main
• Deploy immediately after merge

Trunk-Based Development (High-Velocity Teams)

Best for teams with strong CI/CD and feature flags.

main (trunk)
  │
  ├── short-lived feature (1-2 days max)
  ├── short-lived feature
  └── short-lived feature

Rules:

• Everyone commits to main or very short-lived branches
• Feature flags hide incomplete work
• CI must pass before merge
• Deploy multiple times per day

GitFlow (Complex, Release-Cycle Driven)

Best for scheduled releases and enterprise projects.

main (production releases)
  │
  └── develop (integration branch)
        │
        ├── feature/user-auth
        ├── feature/payment
        │
        ├── release/1.0.0    → merge to main and develop
        │
        └── hotfix/critical  → merge to main and develop

Rules:

• main contains production-ready code only
• develop is the integration branch
• Feature branches from develop, merge back to develop
• Release branches from develop, merge to main and develop
• Hotfix branches from main, merge to both main and develop

When to Use Which

Strategy	Team Size	Release Cadence	Best For
GitHub Flow	Any	Continuous	SaaS, web apps, startups
Trunk-Based	5+ experienced	Multiple/day	High-velocity teams, feature flags
GitFlow	10+	Scheduled	Enterprise, regulated industries

Commit Messages

Conventional Commits Format

<type>(<scope>): <subject>

[optional body]

[optional footer(s)]

Types

Type	Use For	Example
feat	New feature	feat(auth): add OAuth2 login
fix	Bug fix	fix(api): handle null response in user endpoint
docs	Documentation	docs(readme): update installation instructions
style	Formatting, no code change	style: fix indentation in login component
refactor	Code refactoring	refactor(db): extract connection pool to module
test	Adding/updating tests	test(auth): add unit tests for token validation
chore	Maintenance tasks	chore(deps): update dependencies
perf	Performance improvement	perf(query): add index to users table
ci	CI/CD changes	ci: add PostgreSQL service to test workflow
revert	Revert previous commit	revert: revert "feat(auth): add OAuth2 login"

Good vs Bad Examples

# BAD: Vague, no context
git commit -m "fixed stuff"
git commit -m "updates"
git commit -m "WIP"

# GOOD: Clear, specific, explains why
git commit -m "fix(api): retry requests on 503 Service Unavailable

The external API occasionally returns 503 errors during peak hours.
Added exponential backoff retry logic with max 3 attempts.

Closes #123"

Commit Message Template

Create .gitmessage in repo root:

# <type>(<scope>): <subject>
# # Types: feat, fix, docs, style, refactor, test, chore, perf, ci, revert
# Scope: api, ui, db, auth, etc.
# Subject: imperative mood, no period, max 50 chars
#
# [optional body] - explain why, not what
# [optional footer] - Breaking changes, closes #issue

Enable with: git config commit.template .gitmessage

Merge vs Rebase

Merge (Preserves History)

# Creates a merge commit
git checkout main
git merge feature/user-auth

# Result:
# *   merge commit
# |\
# | * feature commits
# |/
# * main commits

Use when:

• Merging feature branches into main
• You want to preserve exact history
• Multiple people worked on the branch
• The branch has been pushed and others may have based work on it

Rebase (Linear History)

# Rewrites feature commits onto target branch
git checkout feature/user-auth
git rebase main

# Result:
# * feature commits (rewritten)
# * main commits

Use when:

• Updating your local feature branch with latest main
• You want a linear, clean history
• The branch is local-only (not pushed)
• You're the only one working on the branch

Rebase Workflow

# Update feature branch with latest main (before PR)
git checkout feature/user-auth
git fetch origin
git rebase origin/main

# Fix any conflicts
# Tests should still pass

# Force push (only if you're the only contributor)
git push --force-with-lease origin feature/user-auth

When NOT to Rebase

# NEVER rebase branches that:
- Have been pushed to a shared repository
- Other people have based work on
- Are protected branches (main, develop)
- Are already merged

# Why: Rebase rewrites history, breaking others' work

Pull Request Workflow

PR Title Format

<type>(<scope>): <description>

Examples:
feat(auth): add SSO support for enterprise users
fix(api): resolve race condition in order processing
docs(api): add OpenAPI specification for v2 endpoints

PR Description Template

## What

Brief description of what this PR does.

## Why

Explain the motivation and context.

## How

Key implementation details worth highlighting.

## Testing

- [ ] Unit tests added/updated
- [ ] Integration tests added/updated
- [ ] Manual testing performed

## Screenshots (if applicable)

Before/after screenshots for UI changes.

## Checklist

- [ ] Code follows project style guidelines
- [ ] Self-review completed
- [ ] Comments added for complex logic
- [ ] Documentation updated
- [ ] No new warnings introduced
- [ ] Tests pass locally
- [ ] Related issues linked

Closes #123

Code Review Checklist

For Reviewers:

• Does the code solve the stated problem?
• Are there any edge cases not handled?
• Is the code readable and maintainable?
• Are there sufficient tests?
• Are there security concerns?
• Is the commit history clean (squashed if needed)?

For Authors:

• Self-review completed before requesting review
• CI passes (tests, lint, typecheck)
• PR size is reasonable (<500 lines ideal)
• Related to a single feature/fix
• Description clearly explains the change

Conflict Resolution

Identify Conflicts

# Check for conflicts before merge
git checkout main
git merge feature/user-auth --no-commit --no-ff

# If conflicts, Git will show:
# CONFLICT (content): Merge conflict in src/auth/login.ts
# Automatic merge failed; fix conflicts and then commit the result.

Resolve Conflicts

# See conflicted files
git status

# View conflict markers in file
# <<<<<<< HEAD
# content from main
# =======
# content from feature branch
# >>>>>>> feature/user-auth

# Option 1: Manual resolution
# Edit file, remove markers, keep correct content

# Option 2: Use merge tool
git mergetool

# Option 3: Accept one side
git checkout --ours src/auth/login.ts    # Keep main version
git checkout --theirs src/auth/login.ts  # Keep feature version

# After resolving, stage and commit
git add src/auth/login.ts
git commit

Conflict Prevention Strategies

# 1. Keep feature branches small and short-lived
# 2. Rebase frequently onto main
git checkout feature/user-auth
git fetch origin
git rebase origin/main

# 3. Communicate with team about touching shared files
# 4. Use feature flags instead of long-lived branches
# 5. Review and merge PRs promptly

Branch Management

Naming Conventions

# Feature branches
feature/user-authentication
feature/JIRA-123-payment-integration

# Bug fixes
fix/login-redirect-loop
fix/456-null-pointer-exception

# Hotfixes (production issues)
hotfix/critical-security-patch
hotfix/database-connection-leak

# Releases
release/1.2.0
release/2024-01-hotfix

# Experiments/POCs
experiment/new-caching-strategy
poc/graphql-migration

Branch Cleanup

# Delete local branches that are merged
git branch --merged main | grep -v "^\*\|main" | xargs -n 1 git branch -d

# Delete remote-tracking references for deleted remote branches
git fetch -p

# Delete local branch
git branch -d feature/user-auth  # Safe delete (only if merged)
git branch -D feature/user-auth  # Force delete

# Delete remote branch
git push origin --delete feature/user-auth

Stash Workflow

# Save work in progress
git stash push -m "WIP: user authentication"

# List stashes
git stash list

# Apply most recent stash
git stash pop

# Apply specific stash
git stash apply stash@{2}

# Drop stash
git stash drop stash@{0}

Release Management

Semantic Versioning

MAJOR.MINOR.PATCH

MAJOR: Breaking changes
MINOR: New features, backward compatible
PATCH: Bug fixes, backward compatible

Examples:
1.0.0 → 1.0.1 (patch: bug fix)
1.0.1 → 1.1.0 (minor: new feature)
1.1.0 → 2.0.0 (major: breaking change)

Creating Releases

# Create annotated tag
git tag -a v1.2.0 -m "Release v1.2.0

Features:
- Add user authentication
- Implement password reset

Fixes:
- Resolve login redirect issue

Breaking Changes:
- None"

# Push tag to remote
git push origin v1.2.0

# List tags
git tag -l

# Delete tag
git tag -d v1.2.0
git push origin --delete v1.2.0

Changelog Generation

# Generate changelog from commits
git log v1.1.0..v1.2.0 --oneline --no-merges

# Or use conventional-changelog
npx conventional-changelog -i CHANGELOG.md -s

Git Configuration

Essential Configs

# User identity
git config --global user.name "Your Name"
git config --global user.email "[e-mail]"

# Default branch name
git config --global init.defaultBranch main

# Pull behavior (rebase instead of merge)
git config --global pull.rebase true

# Push behavior (push current branch only)
git config --global push.default current

# Auto-correct typos
git config --global help.autocorrect 1

# Better diff algorithm
git config --global diff.algorithm histogram

# Color output
git config --global color.ui auto

Useful Aliases

# Add to ~/.gitconfig
[alias]
    co = checkout
    br = branch
    ci = commit
    st = status
    unstage = reset HEAD --
    last = log -1 HEAD
    visual = log --oneline --graph --all
    amend = commit --amend --no-edit
    wip = commit -m "WIP"
    undo = reset --soft HEAD~1
    contributors = shortlog -sn

Gitignore Patterns

# Dependencies
node_modules/
vendor/

# Build outputs
dist/
build/
*.o
*.exe

# Environment files
.env
.env.local
.env.*.local

# IDE
.idea/
.vscode/
*.swp
*.swo

# OS files
.DS_Store
Thumbs.db

# Logs
*.log
logs/

# Test coverage
coverage/

# Cache
.cache/
*.tsbuildinfo

Common Workflows

Starting a New Feature

# 1. Update main branch
git checkout main
git pull origin main

# 2. Create feature branch
git checkout -b feature/user-auth

# 3. Make changes and commit
git add .
git commit -m "feat(auth): implement OAuth2 login"

# 4. Push to remote
git push -u origin feature/user-auth

# 5. Create Pull Request on GitHub/GitLab

Updating a PR with New Changes

# 1. Make additional changes
git add .
git commit -m "feat(auth): add error handling"

# 2. Push updates
git push origin feature/user-auth

Syncing Fork with Upstream

# 1. Add upstream remote (once)
git remote add upstream https://github.com/original/repo.git

# 2. Fetch upstream
git fetch upstream

# 3. Merge upstream/main into your main
git checkout main
git merge upstream/main

# 4. Push to your fork
git push origin main

Undoing Mistakes

# Undo last commit (keep changes)
git reset --soft HEAD~1

# Undo last commit (discard changes)
git reset --hard HEAD~1

# Undo last commit pushed to remote
git revert HEAD
git push origin main

# Undo specific file changes
git checkout HEAD -- path/to/file

# Fix last commit message
git commit --amend -m "New message"

# Add forgotten file to last commit
git add forgotten-file
git commit --amend --no-edit

Git Hooks

Pre-Commit Hook

#!/bin/bash
# .git/hooks/pre-commit

# Run linting
npm run lint || exit 1

# Run tests
npm test || exit 1

# Check for secrets
if git diff --cached | grep -E '(password|api_key|secret)'; then
    echo "Possible secret detected. Commit aborted."
    exit 1
fi

Pre-Push Hook

#!/bin/bash
# .git/hooks/pre-push

# Run full test suite
npm run test:all || exit 1

# Check for console.log statements
if git diff origin/main | grep -E 'console\.log'; then
    echo "Remove console.log statements before pushing."
    exit 1
fi

Anti-Patterns

# BAD: Committing directly to main
git checkout main
git commit -m "fix bug"

# GOOD: Use feature branches and PRs

# BAD: Committing secrets
git add .env  # Contains API keys

# GOOD: Add to .gitignore, use environment variables

# BAD: Giant PRs (1000+ lines)
# GOOD: Break into smaller, focused PRs

# BAD: "Update" commit messages
git commit -m "update"
git commit -m "fix"

# GOOD: Descriptive messages
git commit -m "fix(auth): resolve redirect loop after login"

# BAD: Rewriting public history
git push --force origin main

# GOOD: Use revert for public branches
git revert HEAD

# BAD: Long-lived feature branches (weeks/months)
# GOOD: Keep branches short (days), rebase frequently

# BAD: Committing generated files
git add dist/
git add node_modules/

# GOOD: Add to .gitignore

Quick Reference

Task	Command
Create branch	git checkout -b feature/name
Switch branch	git checkout branch-name
Delete branch	git branch -d branch-name
Merge branch	git merge branch-name
Rebase branch	git rebase main
View history	git log --oneline --graph
View changes	git diff
Stage changes	git add . or git add -p
Commit	git commit -m "message"
Push	git push origin branch-name
Pull	git pull origin branch-name
Stash	git stash push -m "message"
Undo last commit	git reset --soft HEAD~1
Revert commit	git revert HEAD