Lesson 04 — Status, Staging, and Commits

Goal

Make one small change in the practice repository, inspect what changed, and save it in Git history as a commit.

This lesson is deliberately slow. The skill is not typing commands quickly; the skill is knowing what Git knows before you move to the next step.

Mental model

Git tracks three useful questions:

Question	Command	What you learn
What does Git see right now?	git status	Branch, changed files, staged files, and next-step hints
What exactly changed?	git diff	Line-by-line unstaged edits
What is ready to be committed?	git diff --staged	Line-by-line staged edits

Calm habit: Run git status whenever you feel unsure. It is a diagnostic command, not a test.

Core workflow

What these commands mean

git status

Shows what Git knows about your working tree, staging area, current branch, and relationship to GitHub.

git diff

Shows the exact text changes that are not staged yet.

git add filename

Stages a file. Staging means: “include this version of this file in my next commit.”

git diff --staged

Shows the exact text changes currently staged for the next commit.

git commit -m "message"

Creates a saved checkpoint in local Git history.

Important: A commit is local until you push it. A push sends commits to GitHub; it does not create commits from unsaved file changes.

Checklist

1. Start clean

Run:

git status

Expected if nothing is pending:

On branch main
Your branch is up to date with 'origin/main'.

nothing to commit, working tree clean

If Git lists changes, pause and decide whether they belong to this exercise before continuing.

• I know which branch I am on.
• I know whether my working tree is clean or has changes.

2. Make one small change

In git-basics-sql-practice, open:

analysis-notes/visit-count-notes.md

Add one short note about the question an analysis should answer.

Example:

This query should help us confirm whether visit counts changed by county.

Save the file in your editor.

• I made one small file change.
• I saved the file.

3. Check status again

Run:

git status

Expected shape:

Changes not staged for commit:
  modified:   analysis-notes/visit-count-notes.md

This means Git sees a saved file change, but the change is not staged yet.

• I can see the changed file listed.
• I understand this change is not committed yet.

4. Review the exact change

Run:

git diff

Read the output before staging. Look for your new line and check that no unrelated edits appear.

Diffs use a consistent pattern:

- lines removed from the file
+ lines added to the file

• I reviewed the exact lines I changed.
• I do not see unrelated edits.

5. Stage the changed file

Run:

git add analysis-notes/visit-count-notes.md

• I staged the file.

6. Check what is staged

Run:

git status
git diff --staged

Expected shape from git status:

Changes to be committed:
  modified:   analysis-notes/visit-count-notes.md

git diff --staged should show the same intentional change you reviewed earlier.

• I can see that the change is staged.
• I reviewed what will go into the commit.

7. Commit the change

Run:

git commit -m "docs: add analysis note"

Expected shape:

[main abc1234] docs: add analysis note
 1 file changed, 1 insertion(+)

The identifier will be different on your computer.

• I created a local commit.

8. Check status one more time

Run:

git status

Expected shape:

nothing to commit, working tree clean

If Git says your branch is ahead of origin/main by one commit, that is also useful information: your commit exists locally and has not been pushed to GitHub yet.

• Git says there is nothing to commit.
• I know whether this local commit still needs to be pushed.

Good commit messages

A good commit message is short, specific, and written for the next person who reviews the history.

Less helpful	More helpful
updates	docs: add analysis note
fix stuff	docs: clarify visit count query
changes	fix: correct county label typo

More examples:

docs: add analysis note
docs: clarify visit count query
docs: define visit date field
fix: correct county label typo

If something looks wrong

Situation	Safe next step
You changed the wrong file	Do not stage yet. Ask for help or use your editor to undo the file.
git diff is empty but you expected changes	Save the file and check you are in the right repository.
You staged too much	Ask for help before using reset commands.
You are not sure what happened	Run git status and read the branch and file sections aloud.

Completion check

• I can make a small change.
• I can review the change with git diff.
• I can stage a specific file with git add filename.
• I can review staged work with git diff --staged.
• I can commit a change with git commit.
• I understand that commits are local until pushed.