Version Control and Branching

Version control is the foundation of CI/CD. Without a reliable system for tracking changes, collaboration, and history, no pipeline can function. This lesson covers Git fundamentals, branching strategies, and how they support continuous integration.

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Why Version Control Matters for CI/CD

Version control enables:

• Traceability — every change is recorded with an author, timestamp, and message
• Collaboration — multiple developers work on the same codebase simultaneously
• Reversibility — any change can be reverted if it causes problems
• Automation triggers — CI/CD pipelines are triggered by version control events (push, PR, tag)

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Git — The Industry Standard

Git is the dominant version control system used in software development. Created by Linus Torvalds in 2005, it is distributed, fast, and supports powerful branching workflows.

Key Git Concepts

Concept	Description
Repository	A project's complete history and files
Commit	A snapshot of changes with a message
Branch	A pointer to a line of development
Merge	Combining changes from one branch into another
Remote	A shared repository (e.g., on GitHub or GitLab)
Tag	A named reference to a specific commit (e.g., v1.0.0)

Essential Git Commands

# Clone a repository
git clone https://github.com/org/repo.git

# Create and switch to a new branch
git checkout -b feature/add-login

# Stage and commit changes
git add .
git commit -m "Add login page"

# Push changes to remote
git push origin feature/add-login

# Merge a branch
git checkout main
git merge feature/add-login

# Tag a release
git tag -a v1.2.0 -m "Release 1.2.0"
git push origin v1.2.0

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Branching Strategies

Choosing the right branching strategy is critical for CI/CD success. The strategy determines how often code is integrated, how conflicts are managed, and how releases are cut.

1. Trunk-Based Development

The recommended strategy for CI/CD. All developers commit directly to the main branch (trunk) or use very short-lived feature branches (< 1 day).

main: ──●──●──●──●──●──●──●──●──●──●──
         │     │
feature:  └──●──┘   (merged within hours)

Advantages:

• Minimises merge conflicts
• Enables true continuous integration
• Simple to understand
• Works well with feature flags

When to use: Teams practising CI/CD, high-trust environments, trunk-based release cadence.

2. GitFlow

A more structured strategy with dedicated branches for features, releases, and hotfixes. Popularised by Vincent Driessen in 2010.

main:    ──●─────────────●──────────●──
            \             /           /
release:     \──●──●──●──/           /
              \                     /
develop: ──●──●──●──●──●──●──●──●──
              \       /
feature:       └──●──┘

Branch	Purpose	Lifetime
main	Production-ready code	Permanent
develop	Integration branch	Permanent
feature/*	New features	Short-lived
release/*	Release preparation	Temporary
hotfix/*	Production fixes	Temporary

Advantages:

• Clear separation of concerns
• Supports scheduled release cycles
• Suitable for multiple concurrent versions