GH-900 cheat sheet

Exam at a glance

Domain weightings

How much of the exam each domain covers. Spend your study time in proportion — the heavier the domain, the more questions you'll see.

Key terms

Git

Git is a distributed version control system that tracks changes to files and coordinates work among multiple people. Every clone is a full repository with complete history, which is what distinguishes Git from the GitHub platform built on top of it.

GitHub

GitHub is a cloud platform built around Git that adds collaboration, hosting, and automation features to Git repositories. It provides issues, pull requests, Actions, and project management on top of Git version control.

Repository

A repository is the fundamental unit of storage on GitHub that holds a project's files, history, and configuration. Key files include README, LICENSE, CONTRIBUTING, CODEOWNERS, and SECURITY, and a repository can be public, private, or internal.

Commit

A commit is a snapshot of changes recorded in a Git repository, identified by a unique hash and accompanied by a message. Commits form the history of a project and are the units that branches point to.

Branch

A branch is a movable pointer to a line of development in a Git repository, letting work proceed in isolation from the default branch. GitHub Flow uses short-lived feature branches merged back through pull requests.

GitHub Flow

GitHub Flow is a lightweight, branch-based workflow for collaborating on projects. It centers on creating a branch, making commits, opening a pull request, reviewing, and merging to the default branch.

Pull request

A pull request is a GitHub proposal to merge changes from one branch into another, providing a place for review and discussion. It can be linked to issues and gated by required reviews and status checks before merging.

Issue

An issue is a GitHub item used to track tasks, bugs, enhancements, and discussion for a repository. Issues support labels, assignees, milestones, and templates, and can be linked to pull requests.

GitHub Actions

GitHub Actions is GitHub's built-in automation and CI/CD platform that runs workflows in response to repository events. Workflows are defined in YAML and run jobs on hosted or self-hosted runners.

GitHub Copilot

GitHub Copilot is an AI pair-programmer that suggests code and assists development inside editors and GitHub. It offers features such as Agent Mode and multi-model support and comes in Individual, Business, and Enterprise plans.

Codespaces

GitHub Codespaces is a cloud-based development environment configured through dev containers and accessible from the browser or an editor. It lets developers code without setting up a local toolchain, and differs from the lightweight github.dev editor.

GitHub Projects

GitHub Projects is an adaptable planning tool that organizes issues and pull requests into boards, tables, and roadmaps. It supports custom fields, labels, milestones, workflows, and insights for tracking progress.

EMU

EMU (Enterprise Managed Users) is a GitHub Enterprise feature where user accounts are provisioned and controlled by the enterprise's identity provider. Managed users can only interact within the enterprise, giving organizations tighter identity and access control.

Two-factor authentication

Two-factor authentication (2FA) is a security measure that requires a second verification factor in addition to a password when signing in. GitHub supports 2FA and passkeys, and now requires 2FA for many contributors to strengthen account security.

Fork

A fork is a personal copy of another user's repository that lets you propose changes or start your own line of development. Forks are commonly used to contribute to open-source projects through pull requests back to the upstream repository.