Why Version Control, and Your First Repository

Git records snapshots of your project over time. With it you can see what changed, when and why; undo mistakes; work on several ideas at once; and collaborate without emailing zip files. Every professional software team uses it.

One-time setup

git config --global user.name "Ada Lovelace"
git config --global user.email "ada@example.com"
git config --global init.defaultBranch main
git config --global core.editor "code --wait"   # or nano, vim

The three areas

You edit files, stage the changes you want with git add, then commit them with a message. Staging lets you split unrelated edits into separate, clear commits.

Your first repository

mkdir hello-git && cd hello-git
git init
echo "# Hello Git" > README.md
git status                 # README.md is untracked
git add README.md
git status                 # staged, ready to commit
git commit -m "Add README"
git log --oneline          # a1b2c3d Add README

The everyday loop

git status                 # what changed?
git diff                   # exact changes not yet staged
git add app.py             # stage one file
git add -p                 # stage piece by piece (review each change)
git diff --staged          # what will be committed
git commit -m "Validate email on signup"

git add -p is the habit that separates careful developers from everyone else: you review every line before it enters history.

Writing good commit messages

• Start with a short summary in the imperative: "Fix login redirect", not "fixed stuff".
• Keep the summary under about 60 characters.
• If more is needed, leave a blank line, then explain why the change was made.

Limit contact form to 5 posts per hour

Bots were sending hundreds of messages a day. The limit and the
honeypot field stop them without affecting real visitors.

.gitignore: what never to commit

Create .gitignore before your first commit:

.env
.venv/
__pycache__/
*.db
node_modules/
uploads/

Never commit secrets. If a key reaches a public repository, assume bots have already copied it: revoke and rotate it immediately. Deleting the file in a new commit does not remove it from history.

Practice

In the Practice Terminal, complete the First commit mission: git init, git add readme.txt, git commit -m "first commit".

Check yourself

• What is the staging area for?
• Which file stops .env from being committed?
• What should you do if you pushed an API key?