Engineering Craft › Version Control (Git)

Staging Area

Where you choose which changes go into the next commit.

Also known as: index, git index, stage, git add

The staging area (also called the index) is where you assemble the next commit. Git doesn’t commit everything you changed. It commits what you’ve staged.

working directory  ──git add──►  staging area  ──git commit──►  repository (history)
 (your files)                  (the next commit)

git status                  # what changed, and what's staged
git add src/login.py        # stage this file
git add -p                  # stage selected parts of files, interactively
git diff                    # unstaged changes
git diff --staged           # what's staged: what the next commit will contain
git restore --staged file   # unstage (keeps the changes in the file)
git commit -m "Fix login redirect"

Why the extra step

It lets you choose what goes into each commit. If you fixed a bug and also reformatted another file, stage and commit them separately, so each commit is one logical change (atomic commits).

git add -p goes further: it shows each chunk of change, and asks whether to include it. That lets you split even one file across commits.

Reading git status

Changes to be committed:       ← staged: will be in the next commit
Changes not staged for commit: ← modified, but not staged
Untracked files:               ← new files Git doesn't know yet

Common slips

• Forgetting to git add a changed or new file, so the commit lacks it. Check git status before committing.
• Staging too much (git add . includes debug code and stray files). Review with git diff --staged first.
• Editing after staging. A later change to the same file is not in the staged version until you add again.
• Files listed in .gitignore won’t be added by accident.

Shortcut: git commit -a stages modified (not new) tracked files and commits in one go. It’s convenient, but skips the review step.