Glossary

Every concept in this sheet, plus the smaller terms it uses. Select a concept to open its card.

Blobs, trees and hashes: Git stores file contents as blobs, folders as trees and snapshots as commits, each addressed by a hash of its content.
Branches and refs: A branch is just a named pointer to a commit.

Commit: A snapshot of the whole project at one moment, plus an author, a message and a pointer to its parent commit (two parents for a merge).

git add: Stages changes into the index.
git commit: Records the staged snapshot as a new commit on the current branch.
git config: Sets options at three levels: system, global (your user, in ~/.gitconfig) and local (one repository).
git diff: Shows line changes.
git init and git clone: git init turns a folder into a new repository.
git rm and git mv: git rm deletes a file and stages the deletion; git rm --cached stops tracking it but keeps it on disk.
git status: Shows the current branch, how it compares with its upstream, and which files are staged, modified or untracked.

HEAD and detached HEAD: HEAD is the pointer to what you have checked out, normally a branch name.

Working tree: The files you see and edit on disk, checked out from one commit.