Engineering Craft › Version Control (Git)

Commit

A snapshot of changes with a message explaining them.

Also known as: git commit, commits, commit snapshot

A commit is a saved snapshot of your project, with a message saying why you made the change. Your history is a chain of commits, each pointing to the one before.

git status                       # what changed?
git add src/login.py             # choose what goes in the next commit
git commit -m "Reject expired reset tokens"

Each commit records:

• the state of every tracked file at that moment,
• who made it and when,
• your message,
• a pointer to its parent commit(s),
• a unique ID (a hash like a1b2c3d) that identifies it.

Committing is a two-step process on purpose. git add moves changes into the staging area, then git commit records exactly what’s staged. That lets you commit only some of your changes.

Good commit habits

• Commit small and often. Each commit should do one thing and leave the project working (see atomic commits). Small commits are easy to review, undo and understand.
• Write a useful message that explains the why: see commit messages.
• Check what you’re committing. git diff --staged shows exactly what will go in. This catches debug prints and secrets before they’re recorded.
• Commit only what’s yours to commit. Don’t add .env files or build output (see .gitignore).

A commit isn’t shared until you push it. Until then you can still fix the latest one with amend.