Learning GitHub Actions

Chapter 2. How Does Actions Work?

In Chapter 1, you got acquainted at a high level with the overall framework and value of GitHub Actions. In this chapter, we’ll dive into the parts that make up GitHub Actions and how they work together, meaning what kicks them off, what happens when they run, and so on.

As a reminder, in the world of GitHub Actions, actions can refer to the following:

• The entire system for executing automated workflows in response to events
• The actual units of code and related pieces that implement individual actions

Following the convention suggested by GitHub, the book will use GitHub Actions or Actions (with an uppercase “A”) to refer to the system and actions (with a lowercase “a”) to refer to the code units.

To better understand the Actions environment, I’ll provide you with an overview of how the overall flow works. This includes the types of events that can start the automation and a high-level overview of the components that are involved in the execution of the automation. Throughout the chapter, I’ll offer some simple example code. This will give you a solid understanding of how the flow works.

An Overview

At a high level, the GitHub Actions flow is this:

1. Some triggering event happens in a GitHub repository. This event is most often associated with a unique SHA1 (Secure Hashing Algorithm 1) value and a Git reference that resolves to an SHA1 value (a ref), such as a branch. But it may also be an event in GitHub that is not an update to a ref. An example ...