$ man commits
Engineering · Version Control
Commits
A snapshot of your files at a specific point in time with a message explaining what changed.
why it matters
Commits are your paper trail. They tell the story of how you built something. Good commit messages make debugging easier. Bad commit messages make you hate yourself when you're trying to figure out what broke.
how you use it
git commit -m "add user authentication". The message should say what you did and why. Not "fix stuff" or "updates". That's useless.
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