git-workflow-and-versioning

Git Workflow and Versioning

Overview

Git is your safety net. Treat commits as save points, branches as sandboxes, and history as documentation. With AI agents generating code at high speed, disciplined version control is the mechanism that keeps changes manageable, reviewable, and reversible.

When to Use

Always. Every code change flows through git.

Core Principles

Trunk-Based Development (Recommended)

Keep main always deployable. Work in short-lived feature branches that merge back within 1-3 days. Long-lived development branches are hidden costs — they diverge, create merge conflicts, and delay integration. DORA research consistently shows trunk-based development correlates with high-performing engineering teams.

main ──●──●──●──●──●──●──●──●──●──  (always deployable)
        ╲      ╱  ╲    ╱
         ●──●─╱    ●──╱    ← short-lived feature branches (1-3 days)

• Dev branches are costs. Every day a branch lives, it accumulates merge risk.
• Release branches are acceptable. When you need to stabilize a release while main moves forward.
• Feature flags > long branches. Prefer deploying incomplete work behind flags rather than keeping it on a branch for weeks.

1. Commit Early, Commit Often

Each successful increment gets its own commit. Don't accumulate large uncommitted changes.

Work pattern:
  Implement slice → Test → Verify → Commit → Next slice

Not this:
  Implement everything → Hope it works → Giant commit

Commits are save points. If the next change breaks something, you can revert to the last known-good state instantly.

2. Atomic Commits

Each commit does one logical thing:

# Good: Each commit is self-contained
a1b2c3d Add task creation endpoint with validation
d4e5f6g Add task creation form component
h7i8j9k Connect form to API and add loading state
m1n2o3p Add task creation tests (unit + integration)

# Bad: Everything mixed together
x1y2z3a Add task feature, fix sidebar, update deps, refactor utils

3. Descriptive Messages

Commit messages explain the why, not just the what:

# Good: Explains intent
feat: add email validation to registration endpoint

Prevents invalid email formats from reaching the database.
Uses Zod schema validation at the route handler level,
consistent with existing validation patterns in auth.ts.

# Bad: Describes what's obvious from the diff
update auth.ts

Format:

<type>: <short description>

<optional body explaining why, not what>

Types:

• feat — New feature
• fix — Bug fix
• refactor — Code change that neither fixes a bug nor adds a feature
• test — Adding or updating tests
• docs — Documentation only
• chore — Tooling, dependencies, config

4. Keep Concerns Separate

Don't combine formatting changes with behavior changes. Don't combine refactors with features. Each type of change should be a separate commit — and ideally a separate PR:

Separate refactoring from feature work. A refactoring change and a feature change are two different changes — submit them separately. This makes each change easier to review, revert, and understand in history.

5. Size Your Changes

Target ~100 lines per commit/PR. Changes over ~1000 lines should be split.

~100 lines  → Easy to review, easy to revert
~300 lines  → Acceptable for a single logical change
~1000 lines → Split into smaller changes

Branching Strategy

Feature Branches

main (always deployable)
  │
  ├── feature/task-creation    ← One feature per branch
  ├── feature/user-settings    ← Parallel work
  └── fix/duplicate-tasks      ← Bug fixes

• Branch from main (or the team's default branch)
• Keep branches short-lived (merge within 1-3 days)
• Delete branches after merge
• Prefer feature flags over long-lived branches for incomplete features

Branch Naming

feature/<short-description>   → feature/task-creation
fix/<short-description>       → fix/duplicate-tasks
chore/<short-description>     → chore/update-deps
refactor/<short-description>  → refactor/auth-module

Working with Worktrees

For parallel AI agent work, use git worktrees to run multiple branches simultaneously:

# Create a worktree for a feature branch
git worktree add ../project-feature-a feature/task-creation
git worktree add ../project-feature-b feature/user-settings

# Each worktree is a separate directory with its own branch
# Agents can work in parallel without interfering

# When done, merge and clean up
git worktree remove ../project-feature-a

Benefits:

• Multiple agents can work on different features simultaneously
• No branch switching needed (each directory has its own branch)
• If one experiment fails, delete the worktree — nothing is lost
• Changes are isolated until explicitly merged

The Save Point Pattern

Agent starts work
    │
    ├── Makes a change
    │   ├── Test passes? → Commit → Continue
    │   └── Test fails? → Revert to last commit → Investigate
    │
    └── Feature complete → All commits form a clean history

This pattern means you never lose more than one increment of work. If an agent goes off the rails, git reset --hard HEAD takes you back to the last successful state.

Change Summaries

After any modification, provide a structured summary:

CHANGES MADE:
- src/routes/tasks.ts: Added validation middleware to POST endpoint
- src/lib/validation.ts: Added TaskCreateSchema using Zod

THINGS I DIDN'T TOUCH (intentionally):
- src/routes/auth.ts: Has similar validation gap but out of scope
- src/middleware/error.ts: Error format could be improved (separate task)

POTENTIAL CONCERNS:
- The Zod schema is strict — rejects extra fields. Confirm this is desired.
- Added zod as a dependency (72KB gzipped) — already in package.json

Pre-Commit Hygiene

Before every commit:

# 1. Check what you're about to commit
git diff --staged

# 2. Ensure no secrets
git diff --staged | grep -i "password\|secret\|api_key\|token"

# 3. Run tests
npm test

# 4. Run linting
npm run lint

# 5. Run type checking
npx tsc --noEmit

Handling Generated Files

• Commit generated files only if the project expects them (e.g., package-lock.json, Prisma migrations)
• Don't commit build output (dist/, .next/), environment files (.env), or IDE config (.vscode/settings.json unless shared)
• Have a `.gitignore` that covers: node_modules/, dist/, .env, .env.local, *.pem

Using Git for Debugging

# Find which commit introduced a bug
git bisect start
git bisect bad HEAD
git bisect good <known-good-commit>

# View what changed recently
git log --oneline -20
git diff HEAD~5..HEAD -- src/

# Search commit messages for a keyword
git log --grep="validation" --oneline

Release & Versioning

Commits are how you track change; a version is how your consumers track it. The moment anything else depends on your code, "latest on main" stops being a sufficient answer to "what am I running, and is it safe to upgrade?"

Semantic Versioning

Version MAJOR.MINOR.PATCH and let the number carry meaning:

  MAJOR  breaking change — consumers must change their code to upgrade
  MINOR  new functionality, backward-compatible — safe to upgrade
  PATCH  bug fix, backward-compatible — safe to upgrade

The number is a promise. When unsure whether a change is breaking, assume it is; a surprise major is far cheaper than a broken consumer.

Tag the Release

A release is an immutable point in history, not a moving branch. Tag it so it can always be reproduced:

git tag -a v1.4.0 -m "Release 1.4.0"
git push origin v1.4.0

Derive the version from the tag rather than hand-editing it in scattered files.

Keep a Changelog Written for Humans

A changelog is not git log. It's the curated, consumer-facing answer to "what changed and do I care?" — grouped by Added / Changed / Fixed / Deprecated / Removed / Security, newest on top, every entry phrased around user impact.

## [1.4.0] - 2025-06-12
### Added
- Bulk task import via CSV
### Fixed
- Timezone drift in recurring task due dates
### Deprecated
- `GET /v1/tasks/all` — use the paginated `GET /v1/tasks` (removal in 2.0)

Write the entry in the same change that makes the change, while the impact is fresh.

Common Rationalizations

Red Flags

• Large uncommitted changes accumulating
• Commit messages like "fix", "update", "misc"
• Formatting changes mixed with behavior changes
• No .gitignore in the project
• Committing node_modules/, .env, or build artifacts
• Long-lived branches that diverge significantly from main
• Force-pushing to shared branches
• A breaking change shipped under a minor or patch version bump
• A release with no tag, or a version number hand-edited out of sync with the tag
• A user-facing release with no changelog entry

Verification

For every commit:

• [ ] Commit does one logical thing
• [ ] Message explains the why, follows type conventions
• [ ] Tests pass before committing
• [ ] No secrets in the diff
• [ ] No formatting-only changes mixed with behavior changes
• [ ] .gitignore covers standard exclusions

For every release (anything with consumers):

• [ ] The version bump matches the change: breaking → major, additive → minor, fix → patch
• [ ] The release is tagged, and the version is derived from the tag
• [ ] The changelog has a curated, human-readable entry grouped by impact for this version