Git: A Time Machine for Your Code

Git records snapshots of your project so you can look back, undo, and collaborate. Without it, developers emailed folders named final-v3-REAL.zip. With it, every state of your project is one command away.

The repository

A repository ("repo") is a folder Git watches. Turn any project into a repo:

git init

This creates a hidden .git folder — the time machine itself. Your files do not change; Git just starts paying attention.

The three places your code lives

1. Working directory — the files you edit
2. Staging area — changes chosen for the next snapshot
3. Repository history — the permanent snapshots ("commits")

git status          # what has changed? what is staged?
git add index.html  # stage one file
git add .           # stage everything changed
git commit -m "Add navigation bar"    # snapshot the staged changes

Commits are checkpoints, not backups

A commit is a named snapshot with a message explaining why. Good messages complete the sentence "This commit will…":

git commit -m "Fix broken link in the footer"     ✓
git commit -m "stuff"                              ✗ future-you will hate this

Small, frequent commits turn big changes into a readable story — and give you dozens of restore points.

Looking back

git log --oneline   # the history, one line per commit

Made a mess before committing? git status tells you the state; the history keeps everything safe that you did commit. This course's own repo has dozens of commits — run git log --oneline on any real project and read it like a diary.

What you learned

• git init starts the time machine
• edit → git status → git add → git commit -m
• Commit messages explain why, in present tense
• git log reads the history

Next: branches — experiment without breaking the main line.