Trunk-Based Development

Also Known As

TL;DR

Explanation

Trunk-Based Development (TBD) requires developers to commit to the main branch at least once per day, keeping branches short-lived (hours, not weeks). This forces continuous integration — conflicts surface immediately rather than at merge time. Incomplete features are hidden behind feature flags. TBD reduces merge conflicts, improves team visibility, and enables true continuous deployment. It requires a comprehensive automated test suite and discipline around feature flags. Google, Facebook, and Netflix use variants of TBD at scale. It contrasts with GitFlow, where feature branches can live for weeks.

Common Misconception

Why It Matters

Common Mistakes

• Feature branches that live longer than 1-2 days — divergence makes merges painful.
• Not using feature flags to hide incomplete work — trunk-based requires deploying incomplete features safely.
• Skipping code review for small changes — small changes still need review; pair programming is an alternative.
• Confusing trunk-based development with no branching — short-lived branches are fine; long-lived ones are not.

Code Examples

# Long-lived feature branch — anti-pattern:
git checkout -b feature/new-payment-system
# 6 weeks of development
# 847 files changed
# Merge conflict hell with main

# Trunk-based:
git checkout -b feature/payment-step-1  # 1 day max
# Small, releasable increment behind a feature flag
git merge main  # Easy — only 1 day of divergence

# Trunk-based: all devs commit to main (or short-lived branches <1 day)

# Feature in progress but not ready → hide behind a flag
# 1. Create branch, work, push small commits daily
git checkout -b feat/new-checkout
# 2. Merge to main within a day — feature flag hides incomplete work
git checkout main && git merge feat/new-checkout

# Feature flag keeps it off for users until complete
if (\$this->flags->isEnabled('new_checkout', \$user)) {
    return \$this->newCheckout->handle(\$cart);
}
return \$this->legacyCheckout->handle(\$cart);

# CI runs on every push to main — must stay green
# If you break main, fix forward or revert immediately

References

• ↗ https://trunkbaseddevelopment.com/

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