Software Engineering at Google

Chapter 16. Version Control and Branch Management

Written by Titus Winters

Edited by Lisa Carey

Perhaps no software engineering tool is quite as universally adopted throughout the industry as version control. One can hardly imagine any software organization larger than a few people that doesn’t rely on a formal Version Control System (VCS) to manage its source code and coordinate activities between engineers. 

In this chapter, we’re going to look at why the use of version control has become such an unambiguous norm in software engineering, and we describe the various possible approaches to version control and branch management, including how we do it at scale across all of Google. We’ll also examine the pros and cons of various approaches; although we believe everyone should use version control, some version control policies and processes might work better for your organization (or in general) than others. In particular, we find “trunk-based development” as popularized by DevOps¹ (one repository, no dev branches) to be a particularly scalable policy approach, and we’ll provide some suggestions as to why that is.

What Is Version Control?

Note

This section might be a little basic for many readers: use of version control is, after all, fairly ubiquitous. If you want to skip ahead, we suggest jumping to the section “Source of Truth”.

A VCS is a system that tracks revisions (versions) of files over time. A VCS maintains some metadata about the set of files being managed, and collectively ...