Branching Strategies

Introduction

Branching strategies define how code flows through the CD Model's 12 stages. This article provides detailed branching flows for the two primary implementation patterns:

• Release Approval (RA): Uses release branches for validation and approval before production
• Continuous Deployment (CDe): Deploys directly from trunk without release branches

See CD Variants for guidance on choosing between RA and CDe.

Release Approval (RA) Pattern

Pattern Overview

The RA pattern uses release branches to isolate releases for validation and approval:

• Enables trunk to continue evolving during release validation
• Allows critical fixes on release branch without trunk changes
• Provides stable release candidate for approval
• Maintains audit trail for regulated environments

Best for: Regulated systems, high-risk applications, systems requiring formal approvals

Stage Flow for RA Pattern

Stages 1-3: Topic Branch Development:

Stages 4-7: Trunk Integration and Testing:

Stages 8-12: Release Branch Flow:

Release Branch Lifecycle

Creation (Stage 8):

git checkout main
git pull origin main
git checkout -b release/10
git push origin release/10

Validation (Stage 9):

• Deploy release branch to PLTE
• Run regression test suite
• Review quality metrics
• Collect evidence (IV, OV, PV)
• Obtain formal approval

Maintenance:

• Release branch stays active until superseded
• Critical fixes applied via cherry-picking (see Cherry-Picking)
• Eventually archived when release is deprecated

RA Pattern Summary

Time Expectations:

• Topic branch: Hours to 2 days
• Trunk testing (Stages 4-7): 1-2 days
• Release branch validation (Stages 8-9): 1-3 days
• Total: 1-2 weeks from commit to production

Continuous Deployment (CDe) Pattern

Pattern Overview

The CDe pattern deploys directly from trunk without release branches:

• Maximizes deployment speed (hours instead of weeks)
• Relies on comprehensive automated testing
• Uses feature flags for runtime control
• Requires mature DevOps practices

Best for: Non-regulated systems, internal tools, teams with mature automation

Stage Flow for CDe Pattern

Stages 1-3: Identical to RA pattern.

Stages 4-7: Trunk Integration and Testing:

Key Differences from RA:

• Stage 6: Faster execution (1-2 hrs vs 2-8 hrs)
• Stage 7: Often automated or skipped
• Higher reliance on automated quality gates

Stages 8-12: Direct Deployment from Trunk:

No Release Branches

The CDe pattern eliminates release branches entirely:

• Trunk is always production-ready
• Deploy directly from trunk
• Feature flags control feature exposure
• Fix-forward or rollback if issues arise

Benefits: Faster deployment, simpler branching model, less overhead

Tradeoffs: Requires higher confidence in trunk, comprehensive testing, and feature flags

Fixing Bugs in Production

Approach 1: Fix-Forward (Preferred)

Create topic branch, implement fix, fast-track through stages, deploy.

Approach 2: Rollback

Roll back to previous version while implementing proper fix.

Approach 3: Feature Flag Kill Switch

Disable problematic feature via flag, fix at normal pace, re-enable.

CDe Pattern Summary

Topic Branch → (Squash Merge) → Trunk → (Tag) → Production

Time Expectations:

• Topic branch: Hours to 1 day
• Trunk testing (Stages 4-7): 2-4 hours
• Deployment (Stages 8-10): Minutes
• Total: 2-4 hours from commit to production

Pipeline Architecture

Both patterns benefit from separating pipeline concerns:

Three layers:

1. Orchestration (YAML): Agent provisioning, parallelization, artifact management
2. Scripting (CLI): Build/test/deploy logic, executable locally
3. Configuration (yml files): Environment-specific settings

This separation enables local development, easier testing, and clearer maintenance.

Pipeline by Branch Type

RA Pattern:

• Topic branch triggers Stages 2-3
• Trunk commit triggers Stages 4-7
• Release branch triggers Stages 8-10
• Manual approval required at Stage 9

CDe Pattern:

• Topic branch triggers Stages 2-3
• Trunk commit triggers Stages 4-10 (automated)
• No release branch pipeline
• Automated approval at Stage 9

Comparison Summary

Branch Type Usage

When to Use Each Pattern

Use RA Pattern when:

• Subject to regulatory oversight
• High-risk system (safety, health, critical operations)
• Requires formal audit trail
• Needs documented approvals

Use CDe Pattern when:

• Non-regulated environment
• Internal tools or low-risk systems
• Mature DevOps practices
• Comprehensive automated testing
• Feature flags implemented

Best Practices

RA Pattern Specific

• Create release branches from trunk only
• Only critical fixes allowed on release branch
• Always fix on trunk first, cherry-pick to release (see Cherry-Picking)
• Archive release branch when superseded

CDe Pattern Specific

• Use feature flags for all incomplete features (see Feature Hiding)
• Implement kill switches for high-risk features
• Gradual rollout (1% → 10% → 50% → 100%)
• Maintain previous version artifacts for rollback

Next Steps

• CD Variants - Choosing between RA and CDe
• Trunk-Based Development - Core principles
• Branch Types - Branch definitions
• Cherry-Picking - Moving fixes between branches
• Dependency Management - Implicit vs pinned dependencies

Tutorials | How-to Guides | Explanation | Reference

You are here: Explanation — understanding-oriented discussion that clarifies concepts.