Glossary

Complete glossary of terms used throughout this handbook.

A

Atomic commit A commit that contains exactly one logical change. Each commit should be independently understandable and should not mix unrelated modifications.

Author (commit) The person who originally wrote the code change. Recorded in every commit alongside the timestamp.

B

Base branch The branch a Pull Request targets. In this group, the base branch is always main.

Branch A movable pointer to a commit. Branches allow parallel lines of development. Creating a branch is cheap and instant in Git.

Branch protection GitHub settings that prevent direct pushes to a branch and require Pull Requests and approvals before merging. Applied to main in all group repositories.

C

Checkout The act of switching to a different branch or restoring a file to a previous state. git checkout branch-name switches your working directory to that branch.

Clone A one-time operation that downloads a remote repository to your local machine, including the full commit history.

Commit A saved snapshot of staged changes. Contains the diff, author, timestamp, message, and a reference to the parent commit.

Commit hash (SHA) A unique 40-character hexadecimal identifier for each commit (e.g., a3f2c91...). Usually abbreviated to the first 7–8 characters.

Compare branch The feature branch being proposed in a Pull Request (the branch containing new changes).

Conflict → see Merge conflict

D

Default branch The branch that GitHub shows by default when visiting a repository. In this group, always main.

Diff A display of the exact lines changed between two states. git diff shows unstaged changes; git diff --staged shows staged changes.

Draft PR A Pull Request explicitly marked as not ready for final review. Used to share work-in-progress and receive early feedback.

F

Fast-forward merge A merge where the target branch simply advances its pointer because no divergence occurred. Results in no merge commit.

Fetch Downloading new commits and branch information from the remote without modifying your local branches. git fetch origin.

Feature branch A branch created for a specific task. Named with a prefix like feature/, bugfix/, docs/, etc. Deleted after the corresponding PR is merged.

Force push Overwriting the remote branch history with your local history. Required after rebasing. Always use --force-with-lease, never --force.

Fork A copy of a repository under your own GitHub account. Not used in this group — students clone directly.

G

Git A distributed version control system. Runs locally on your machine. Created by Linus Torvalds in 2005.

GitHub A web platform that hosts Git repositories and provides collaboration tools (Pull Requests, Issues, code review). The group uses GitHub exclusively.

.gitignore A file listing patterns of files that Git should not track. Located at the root of the repository.

H

HEAD A special pointer that indicates your current position in the repository. Usually points to the tip (latest commit) of your current branch.

Hunk A contiguous section of changed lines in a diff. git add -p lets you stage individual hunks.

I

Index → see Staging area

L

Label (GitHub) A tag applied to Issues and Pull Requests to categorise them. Examples: type: feature, priority: high, status: needs-review.

M

main The primary branch of a repository. Protected; all changes arrive via Pull Requests. Represents the canonical, always-working state of the code.

Merge The act of integrating one branch's commits into another.

Merge commit A special commit created when merging two diverged branches. Has two parent commits. The group avoids these on main by using squash merge.

Merge conflict A situation where two branches have both modified the same lines in a file, and Git cannot automatically decide which version is correct. Must be resolved manually.

Milestone (GitHub) A group of Issues and Pull Requests associated with a deadline or goal (e.g., "Paper Submission v2").

O

origin The conventional name for the default remote — the GitHub repository you cloned from.

P

PR → see Pull Request

Pull git pull fetches new commits from the remote and integrates them into your current local branch. Equivalent to git fetch + git merge.

Pull Request (PR) A proposal on GitHub to merge a feature branch into main. The venue for code review, discussion, and approval before changes are accepted.

Push Sending local commits to the remote (GitHub). git push origin feature/task.

R

Rebase Replaying commits from one branch on top of another. The group uses rebase to update feature branches with the latest main. Produces a linear history.

Remote A named reference to a repository hosted elsewhere (on GitHub). The default remote is named origin.

Repository (repo) A directory tracked by Git. Contains all project files and their complete history, stored in the .git/ subdirectory.

Review (code review) The process of a colleague reading a Pull Request, leaving feedback, and approving or requesting changes.

S

Squash merge A merge strategy that combines all commits on a feature branch into a single commit on the target branch. The group uses squash merge for all PRs into main.

SSH (Secure Shell) A cryptographic protocol used to authenticate with GitHub. The group uses SSH key-based authentication exclusively.

Staging area (index) A preparatory zone between your working directory and the repository. git add moves changes here; git commit records them permanently.

Stash Temporary storage for uncommitted changes. git stash saves changes; git stash pop restores them.

T

Tag A permanent, named pointer to a specific commit. Used to mark releases and paper-submission states. Tags are never deleted.

Tracking branch A local branch linked to a remote branch. git push -u sets the upstream tracking.

U

Upstream The remote branch that a local branch tracks. Set with git push -u origin branch-name.

W

Working directory The actual files in your project folder, as you see them in your editor. Distinct from the staging area and the repository.