Domain review: Git and GitHub basics

On Wednesday, April 14, Owen took the practice assessment for the first time, as a baseline, before the lunchtime session. He answered 37 of 50 questions correctly, and he logged every question he missed or guessed. Seven of the thirteen misses came from areas he had expected, modern development and project management, but three came from Git and GitHub basics, which he thought he knew best. "That is the area worth a quarter of the exam," Priya said, "so we start there." This lesson reviews the first and largest area of the outline: version control, Git and GitHub, the core concepts, accounts and organizations, GitHub Flow, Markdown, and GitHub Desktop and GitHub Mobile.

What version control is for

A version control system records changes to files over time, so you can see who changed what, when and why, return to an earlier state, and work on changes in parallel without overwriting each other. Its benefits come up repeatedly in exam questions: a complete history, the ability to undo or compare changes, collaboration without emailing copies, traceability of every change to a person and a reason, and backup, because every copy of a Git repository holds the full history. At Tidewater, the guidebook text had once lived in shared folders with names such as "coastal-hikes-FINAL-v3-Grace-edits". Version control replaced that with one history everyone could read.

Git is a distributed version control system. Every person who clones a repository gets the whole history on their own computer, can commit without a network connection, and shares work by pushing and pulling. A centralized system, by contrast, keeps the history on one server and needs a connection for most operations. Questions sometimes ask for the advantage of a distributed design: working offline, speed, and no single point of failure.

Git versus GitHub

The single most tested distinction in this area is between Git and GitHub. Git is open source software that tracks changes in a repository. It runs on your computer and works without GitHub at all. GitHub is a cloud platform that hosts Git repositories and adds collaboration around them: pull requests, issues, discussions, Projects, Actions, Codespaces, Copilot, security features, organizations and permissions. Other services also host Git repositories; Git does not depend on any one of them.

Repositories, commits and branches

A repository is a project's folder of files together with its full history. A commit is a saved snapshot of changes, with an author, a date, a message and a unique identifier, called a hash. Commits form a chain, each pointing to its parent, so the history can be replayed. A branch is a movable pointer to a commit, used to work on a change separately; the default branch, usually called main, holds the project's accepted work. Merging combines a branch back into another. A clone is a full local copy of a repository, and a remote is a named link to another copy, usually called origin for the one on GitHub.

git switch -c fix-tide-times
# edit the file
git add coastal/chapter-4.md
git commit -m "Correct tide times for Cape Enrage walk"
git push -u origin fix-tide-times

Remember the staging area between editing and committing: git add chooses which changes go into the next commit, so one commit can contain a coherent change and leave unrelated edits for later. The exam may also mention .gitignore, a file listing paths Git should not track, such as build output or files with local settings.

Accounts, organizations and enterprises

GitHub has three kinds of account. A personal account belongs to one person and owns their repositories. An organization is a shared account that owns repositories for a team or company, with members, teams and permissions; people join it with their personal accounts. An enterprise account sits above several organizations, for large companies that need central policies, billing and identity management. The outline also expects you to recognize the plans: GitHub Free, Pro, Team and Enterprise, covered in MSBA-161 lesson 10, and the two ways to run Enterprise: GitHub Enterprise Cloud on GitHub.com and GitHub Enterprise Server, installed on a company's own infrastructure.

One person has one personal account and can belong to many organizations. A common distractor suggests creating a second personal account for work; GitHub's terms allow one free personal account per person in most cases, and the normal pattern is to use one account and join organizations with it. Companies that need complete control of identities use Enterprise Managed Users, reviewed in lesson 8.

GitHub Flow

GitHub Flow is GitHub's lightweight branching model. It has one long-lived branch, main, which is always deployable. For any change: create a branch from main with a descriptive name, make commits, open a pull request, discuss and review it, make further commits in response, and merge when it is approved and its checks pass, then delete the branch. The exam asks about the order of these steps and about why each exists: the branch keeps main safe, the pull request makes the change visible and reviewable, and merging completes it.

Markdown

Markdown is a simple formatting language for text. GitHub uses GitHub Flavored Markdown in README files, issues, pull requests, discussions, comments and wikis. The outline wants you to use it for clear communication, so expect questions on what common syntax produces.

Mentions and references are where Markdown meets collaboration. Typing @priya-nair in a comment notifies Priya; typing @tidewater-guides/editors notifies a whole team; typing #42 links to issue or pull request 42 in the same repository. Lesson 5 returns to keywords such as closes #42, which link a pull request to an issue and close it on merge.

GitHub Desktop and GitHub Mobile

GitHub Desktop is a free application for Windows and macOS that does common Git work through a graphical interface: cloning, branching, committing, pushing, pulling and resolving simple conflicts. It suits people who prefer not to use the command line, which is why Grace uses it. GitHub Mobile, for iOS and Android, is for staying in touch away from a computer: reading and replying to notifications, reviewing and merging pull requests, managing issues and browsing code. It is not a coding environment. The exam asks which tool fits a situation, so the key distinction is that Desktop does Git work on your computer and Mobile manages GitHub activity on a phone.

Where a change lives

Several baseline questions turned on where a change is at a given moment. Priya drew it as four places. The working directory holds the files as you edit them. The staging area holds the changes chosen for the next commit. The local repository holds your commits on your own computer. The remote repository on GitHub holds the commits you have pushed. A change moves from left to right with git add, git commit and git push, and teammates' work moves the other way with git pull. If a question says a colleague cannot see your commit on GitHub, the likely answer is that it was committed but not pushed; if a file is missing from a commit, it was probably edited but not staged.

The history itself is also worth a moment. Every commit records its parent, so the history of any branch can be read back to the first commit. Comparing two commits shows a diff, the lines added and removed. Undoing a change in a shared history is usually done with a new commit that reverses it, so the record stays honest, rather than by rewriting commits others have already pulled. Foundations questions stay at that level: knowing that history can be compared and reversed, not the details of every reset option.

Owen's three misses

Owen's three baseline misses in this area turned out to be typical. One confused cloning with forking: a clone is a local copy; a fork is a copy of a repository under another GitHub account. One asked which account type gives central policies across several organizations, and he chose organization rather than enterprise. The third asked what GitHub Mobile can do, and he wrongly ticked editing code in a dev container. All three were distinctions between similar things, which is exactly where distractors live. He added each pair to a "confusables" page in his notes, which lesson 10 expands into a full list.