General

Workflows

– it runs one or more jobs.
– it is defined by a YAML file located in to your github repository and will run when triggered by an event in your repository, or they can be triggered manually, or at a defined schedule.
– a repository can have one or more workflows.
Each of which can perform a different set of jobs all the same but in a specific and environment.
– workflows yaml files are defined in the .github/workflows directory of the repository.
– a workflow can reference another workflow.

Events

– it is a specific event that triggers a workflow run.
For example: someone creates a pull request, opens an issue, or pushes a commit to a repository.
These are events triggered inside the repository.
– you can also generate an external event to trigger a workflow by posting to the REST API, or execute the workflow manually.

Jobs

– it is a set of steps in a workflow that is executed on the same runner.
– By default, jobs have no dependencies and run in parallel with each other.
– You can configure a job as dependent of other jobs.
When a job depends on another job, it will wait for the dependent job to complete before it can run.

Steps

– A step is:
* either a shell script that will be executed
* or an action that will be run.

– steps are executed in order and are dependent on each other.
– since each step is executed on the same runner, you can share data from one step to another.
For example, you can have a step that create some files (ex: build,tests execution…) followed by a step that use this files (ex: check the quality of the build, generate test reports).

Actions

– it is a custom addon/extension in GitHub Actions that performs a relatively complex but frequently repeated task.
– it helps reduce the duplication code that you write in your workflow files.
– An action can do many things such as: pull your git repository, set up your build environment or build your application.
– You can write your own actions, or use them available in the GitHub Marketplace.

Runners

– it is a server that runs your workflows when they’re triggered.
– each runner can run a single job at a time.
– GitHub provides Ubuntu Linux, Microsoft Windows, and macOS runners.

Expressions

An expression can be any combination of literal values, references to a context, or functions.
You can combine literals, context references, and functions using operators.
Syntax:
${{ <expression> }}
Example:
${{ github.actor }}

        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}

jobs:
  maven-test:
    if: false

Note: When you use expressions in an if conditional, you may omit the expression syntax.