Atomic Commit

Replacing a file so that readers and crashes see either the complete old version or the complete new one, never a half-written mix, by writing a temporary file and renaming it over the original.

Copying the change from one commit onto another branch as a new commit, the standard way to backport a fix without merging everything else that came with it.

A second person reading a change before it lands, and the practices that make it worth the time.

A recorded snapshot of a project with a message explaining it.

The note attached to each change in version control, conventionally a short summary line and a body explaining why, which becomes the main record of intent for anyone who later wonders why the code is the way it is.

A lightweight convention giving commit messages a machine-readable type and scope.

The listing of changes between two versions of a file, the algorithms that compute it, and the unified format that code review, patches, and merges are built on.

The two basic ways Git joins branches, by sliding a branch pointer forward or by recording a new commit with two parents, and how the choice shapes a project's history.

Finding the commit that introduced a bug by binary search through history, testing the midpoint between a known-good and a known-bad version until one commit remains.

Showing, for every line of a file, the commit and author that last changed it, the starting point for finding out why code is the way it is.

Git's tool for rewriting a series of commits before sharing them, reordering, combining, splitting, and rewording them so the history tells a clear story rather than recording every false start.

The recorded origin of a change or a claim — who made it, when, and on what evidence.

Git's private record of everywhere HEAD and each branch has pointed, the safety net that makes a botched reset, rebase, or deleted branch recoverable for weeks.

A previously working behavior that a change has broken.

Collapsing a branch's commits into one before merging, trading granularity for a clean main history.

The intermediate snapshot in Git between the working files and the next commit, which lets a developer choose exactly which changes go into each commit, down to individual lines.