Event-driven CI/CD that lives in the repo — how workflows are triggered, how jobs and steps run on ephemeral runners, how to use third-party actions safely, and how expressions and variables wire it all together.
6 topics
GitHub Actions turns the repository itself into a CI/CD platform: repo activity emits events, your YAML subscribes to them, and GitHub runs your jobs on fresh, throwaway virtual machines. This chapter installs that mental model first — the event-workflow loop and ephemeral execution — because every later feature, from matrices to caching, is built on it.
The six topics here move from what Actions is, through workflow syntax, triggers, and the job-and-runner execution model, to the two decisions that bite hardest in practice: how you pin third-party actions, and how you handle expressions, contexts, and the env-vs-vars-vs-secrets distinction without leaking credentials or opening an injection hole.