Git Commit Best Practices
Purpose: This skill teaches AI agents to create high-quality commits with clear messages, proper granularity, and effective use of the staging area.
Core Principles
- Atomic Commits - One logical change per commit
- Clear Messages - Follow Conventional Commits format
- Meaningful History - Each commit tells a story
- Smart Staging - Stage only what belongs together
Commit Message Format
Conventional Commits Structure
<type>(<scope>): <subject>
<body>
<footer>Type Categories
# ✓ CORRECT: Use these standard types
feat: # New feature for the user
fix: # Bug fix
docs: # Documentation changes
style: # Formatting, missing semicolons, etc. (no code change)
refactor: # Code change that neither fixes a bug nor adds a feature
perf: # Performance improvement
test: # Adding or updating tests
chore: # Maintenance tasks, dependencies, config
# Examples:
feat(auth): add password reset functionality
fix(api): handle null response in user endpoint
docs(readme): update installation instructions
refactor(parser): simplify token extraction logicSubject Line Guidelines
# ✓ GOOD: Clear, concise, imperative mood
feat(auth): add OAuth2 login support
fix(cart): prevent duplicate items
docs(api): document rate limiting
# ✗ BAD: Vague, past tense, too long
feat(auth): added some authentication stuff
fix(cart): fixed a bug
docs(api): updated the documentation to include information about rate limitingRules:
- Use imperative mood ("add" not "added" or "adds")
- No period at the end
- Keep under 50 characters
- Capitalize first letter after type
- Be specific about what changed
Body Guidelines
# ✓ GOOD: Explains WHY and context
feat(cache): add Redis caching layer
Improves API response time by 80% for frequently accessed data.
Uses Redis with 1-hour TTL for user profile and product catalog
endpoints. Falls back to database if Redis is unavailable.
Related to performance optimization initiative.
# ✗ BAD: Just repeats the subject
feat(cache): add Redis caching layer
Added Redis caching.When to include body:
- Why the change was needed
- How it solves the problem
- Any important implementation decisions
- Side effects or limitations
- Related issues or context
When to skip body:
- Self-explanatory changes (e.g., "fix(typo): correct variable name")
Footer Guidelines
# Breaking changes
feat(api): change user endpoint response format
BREAKING CHANGE: User API now returns camelCase instead of snake_case.
Migration guide: https://docs.example.com/migration/v2
# Issue references
fix(auth): prevent token expiration race condition
Closes #123
Refs #456
# Co-authors
feat(search): implement full-text search
Co-authored-by: Jane Doe <jane@example.com>Atomic Commits
What is an Atomic Commit?
Definition: One commit = one logical change
# ✓ GOOD: Atomic commits
git commit -m "feat(auth): add login endpoint"
git commit -m "feat(auth): add logout endpoint"
git commit -m "test(auth): add login tests"
# ✗ BAD: Non-atomic commit
git commit -m "feat(auth): add login, logout, password reset, and tests"Benefits
- Easy to review - Reviewer focuses on one change
- Easy to revert - Undo specific change without affecting others
- Easy to cherry-pick - Apply specific change to another branch
- Clear history - Each commit has clear purpose
How to Create Atomic Commits
# ✓ CORRECT: Stage related changes only
# You made changes to auth.js, api.js, and tests.js
# Commit 1: Feature implementation
git add src/auth.js src/api.js
git commit -m "feat(auth): add token refresh mechanism"
# Commit 2: Tests
git add tests/auth.test.js
git commit -m "test(auth): add token refresh tests"
# ✗ WRONG: Stage everything together
git add .
git commit -m "feat(auth): add token refresh and tests"Decision Tree: Should This Be One Commit?
Does this change have a single, clear purpose?
├─ YES → Can it be described in one sentence?
│ ├─ YES → One commit ✓
│ └─ NO → Multiple commits
│
└─ NO → Multiple commits
Examples:
├─ "Add login validation" → One commit ✓
├─ "Add login and signup" → Two commits
└─ "Add login, fix bug, update docs" → Three commitsStaging Strategies
Strategy 1: Partial File Staging
# You changed multiple things in one file
# Only stage the lines related to current commit
git add -p src/app.js
# Interactive prompts:
# y - stage this hunk
# n - don't stage this hunk
# s - split into smaller hunks
# e - manually edit the hunk
# Then commit only staged changes
git commit -m "feat(app): add error handling"
# Stage and commit remaining changes separately
git add -p src/app.js
git commit -m "refactor(app): extract validation logic"Strategy 2: Multiple Commits from Unstaged Work
# ✓ WORKFLOW: Create multiple atomic commits from current changes
# Check what changed
git status
git diff
# Commit 1: Feature A
git add src/feature-a.js src/utils.js
git commit -m "feat(feature-a): implement feature A"
# Commit 2: Feature B
git add src/feature-b.js
git commit -m "feat(feature-b): implement feature B"
# Commit 3: Tests
git add tests/
git commit -m "test: add tests for features A and B"Strategy 3: Amend Last Commit
# Use case: You forgot to include a file in the last commit
# ✓ CORRECT: Amend if commit is NOT pushed yet
git add forgotten-file.js
git commit --amend --no-edit
# OR update the commit message too
git commit --amend -m "feat(auth): add login endpoint and middleware"
# ✗ WRONG: Amend if commit is already pushed
# This rewrites history and causes problems for collaborators
# If already pushed, create new commit instead:
git add forgotten-file.js
git commit -m "feat(auth): add missing middleware file"Common Workflows
Workflow 1: Making a Feature Commit
# 1. Check current state
git status
git diff
# 2. Stage related changes only
git add src/feature.js src/api.js
# 3. Review what will be committed
git diff --staged
# 4. Commit with conventional format
git commit -m "feat(feature): add user profile customization
Allows users to customize avatar, bio, and theme preferences.
Settings are persisted to user preferences API endpoint.
Closes #234"
# 5. Verify commit
git log -1 --statWorkflow 2: Making Multiple Atomic Commits
# You worked on multiple things, now need to commit separately
# 1. Check all changes
git status
# 2. First commit: Core feature
git add src/core.js
git commit -m "feat(core): add data validation layer"
# 3. Second commit: API integration
git add src/api.js
git commit -m "feat(api): integrate validation with endpoints"
# 4. Third commit: Tests
git add tests/
git commit -m "test(validation): add comprehensive validation tests"
# 5. Fourth commit: Documentation
git add docs/
git commit -m "docs(validation): document validation rules"Workflow 3: Fixing a Bug
# ✓ GOOD: Clear bug fix commit
git add src/buggy-file.js
git commit -m "fix(cart): prevent duplicate items on double-click
Added debounce to 'Add to Cart' button and server-side duplicate
check. Prevents race condition when users click rapidly.
Fixes #567"
# Include:
# - What the bug was
# - How you fixed it
# - Issue referenceWorkflow 4: Amending vs New Commit Decision
Did I already push this commit?
├─ NO → Safe to amend
│ └─> git commit --amend
│
└─ YES → Create new commit instead
└─> git commit -m "fix: ..."
Is this a fixup for recent commit?
└─> Consider git commit --fixup=<sha>
Then use git rebase -i --autosquash before pushingWorkflow 5: Refactoring Commits
# ✓ GOOD: Separate refactoring from behavior changes
# Commit 1: Pure refactor (no behavior change)
git add src/parser.js
git commit -m "refactor(parser): extract token validation to separate function
No behavior change. Makes code more testable and readable."
# Commit 2: Behavior change
git add src/parser.js
git commit -m "feat(parser): add support for nested tokens
Now supports tokens in format {{parent.child.value}}"
# Why separate?
# - Easy to verify refactor doesn't change behavior
# - Easy to revert feature without losing refactor
# - Clear historyCommon Mistakes to Avoid
Mistake 1: Vague Commit Messages
# ✗ BAD: No context
git commit -m "update"
git commit -m "fix bug"
git commit -m "changes"
git commit -m "wip"
# ✓ GOOD: Clear and specific
git commit -m "feat(auth): add JWT token expiration check"
git commit -m "fix(api): handle null values in user profile endpoint"
git commit -m "refactor(parser): simplify regex patterns"
git commit -m "docs(readme): add Docker setup instructions"Mistake 2: Mixing Unrelated Changes
# ✗ BAD: Multiple unrelated changes in one commit
git add .
git commit -m "feat: add login, fix cart bug, update docs"
# ✓ GOOD: Separate commits
git add src/auth.js
git commit -m "feat(auth): add OAuth login support"
git add src/cart.js
git commit -m "fix(cart): prevent negative quantities"
git add docs/
git commit -m "docs(api): update authentication endpoints"Mistake 3: Committing Debug Code
# ✗ BAD: Leaving console.log, debugger statements
git add src/app.js # Contains console.log debugging
git commit -m "feat(app): add feature"
# ✓ GOOD: Review before committing
git diff --staged # Check for debug code
# Remove debug statements
git add src/app.js
git commit -m "feat(app): add feature"Mistake 4: Too Large or Too Small Commits
# ✗ TOO LARGE: Entire feature in one commit
git commit -m "feat(auth): complete authentication system"
# 50 files changed, 2000+ lines
# ✗ TOO SMALL: Meaningless micro-commits
git commit -m "add semicolon"
git commit -m "fix typo"
git commit -m "add newline"
# ✓ GOOD: Right-sized atomic commits
git commit -m "feat(auth): add login endpoint"
git commit -m "feat(auth): add logout endpoint"
git commit -m "feat(auth): add token refresh mechanism"
git commit -m "test(auth): add authentication tests"Mistake 5: Amending Pushed Commits
# ✗ DANGEROUS: Amending after push
git push origin feature-branch
# Oh, forgot a file!
git add forgotten.js
git commit --amend --no-edit
git push --force origin feature-branch # ← Causes problems!
# ✓ SAFE: New commit instead
git push origin feature-branch
# Oh, forgot a file!
git add forgotten.js
git commit -m "feat(auth): add missing validation helper"
git push origin feature-branchCommit Message Templates
Template for Features
feat(<scope>): <what you added>
<why this feature is needed>
<how it works (if not obvious)>
<any limitations or considerations>
Closes #<issue-number>Template for Bug Fixes
fix(<scope>): <what you fixed>
<what was wrong>
<how you fixed it>
<why this approach>
Fixes #<issue-number>Template for Refactoring
refactor(<scope>): <what you refactored>
No behavior change. <why refactor was needed>
<what improved (readability, performance, maintainability)>Integration with AI Code Generation
When AI agents generate code that needs committing:
1. Analyze Changes Before Committing
# ✓ CORRECT: Check what changed
git status
git diff
# Determine:
# - Is this one logical change or multiple?
# - What type of change? (feat, fix, refactor, etc.)
# - What scope? (auth, api, ui, etc.)2. Create Appropriate Commit Message
# ✓ GOOD: AI-generated message with context
git commit -m "feat(api): add rate limiting middleware
Implements token bucket algorithm with 100 requests/minute limit.
Returns 429 status with Retry-After header when limit exceeded.
Addresses security requirement from issue #789"
# ✗ BAD: Generic AI message
git commit -m "add rate limiting"3. Split Large Changes
# If AI generated multiple files for different purposes:
# ✓ CORRECT: Separate commits
git add src/rate-limiter.js
git commit -m "feat(api): add rate limiting middleware"
git add tests/rate-limiter.test.js
git commit -m "test(api): add rate limiter tests"
git add docs/api.md
git commit -m "docs(api): document rate limiting"
# ✗ WRONG: One large commit
git add .
git commit -m "add rate limiting with tests and docs"Quick Reference Checklist
Before every commit, ask:
- Is this one logical change?
- Did I stage only related files?
- Is my commit message in Conventional Commits format?
- Does the subject line clearly describe what changed?
- Did I explain why (not just what) in the body?
- Did I remove debug code and comments?
- Is this commit NOT already pushed? (if planning to amend)
- Would this be easy to review?
- Would this be easy to revert if needed?
Advanced: Commit Message Psychology
Good commit messages answer:
- What changed? (Subject line)
- Why was it needed? (Body - business reason)
- How does it work? (Body - technical approach)
- What are the side effects? (Body - impacts)
# ✓ EXCELLENT: Answers all questions
feat(search): implement fuzzy search algorithm
Users frequently make typos in search queries, resulting in zero
results and poor experience. Implemented Levenshtein distance-based
fuzzy matching with tolerance of 2 characters.
Performance impact: ~50ms additional latency for searches, acceptable
given improved user experience. Results are cached for 5 minutes.
Closes #456Summary
Key Principles:
- One commit = one logical change (atomic commits)
- Use Conventional Commits format (type, scope, clear subject)
- Explain why, not just what (meaningful commit messages)
- Stage strategically (use
git add -pfor partial staging) - Never amend pushed commits (creates new commit instead)
Quick Command Reference:
git add <file> # Stage specific file
git add -p <file> # Stage parts of file interactively
git diff --staged # Review what will be committed
git commit -m "type(scope): msg" # Commit with message
git commit --amend --no-edit # Amend last commit (if not pushed)
git log -1 --stat # Verify last commitRemember: Commits are documentation of your project's history. Write them for humans who will read them 6 months from now.