action-builder

To build a custom GitHub Action, you define an `action.yml` file to specify inputs and outputs, then implement the logic using composite, Docker, or Node.js runtimes to create reusable workflow steps.

Composite, Docker, and JavaScript GitHub Actions differ by runtime: composite combines multiple steps into one, Docker packages logic in a container, and JavaScript runs directly on the runner, all supporting defined inputs and outputs.

Yes, you can use a composite action to standardize environment setup across repositories by packaging tasks like installing Node.js, configuring npm, and caching dependencies into a single reusable unit.

You define inputs and outputs when creating a GitHub Action by declaring them in the `action.yml` metadata file, which allows your custom workflow steps to receive parameters and return results.

You should package complex CI/CD logic into a self-contained GitHub Action when you need modularity and standardization, allowing you to abstract repetitive tasks into reusable units across your pipelines.