World 1: Save Points

Spot the difference

You will learn: how to see exactly what changed, line by line.

The problem

You edited index.html last night. Now you can’t remember what you changed. One line? Ten lines?

Watch

~/diary $ git diffdiff --git a/index.html b/index.htmlindex 7420d4c..3a6b935 100644--- a/index.html+++ b/index.html@@ -1,4 +1,5 @@ <h1>My Diary</h1> <p>Day 1: I made a repo.</p> <p>Day 2: I learned the box.</p>-<p>TODO: write day 3</p>+<p>Day 3: I made my first commit.</p>+<p>It felt great!</p>

git diff compares your folder with the box. This is a diff. Green + lines are new. Red - lines are gone.

Try it

Tap every line you added.

Tap every added line.

~/diary $ git diff

0 of 2 found

Hint

Added lines start with one +. Skip the +++ line: that is just the file name.

Predict

You run git add index.html. Then you run git diff again. What shows?

Watch

~/diary $ git add index.html~/diary $ git diff~/diary $ git diff --stageddiff --git a/index.html b/index.htmlindex 7420d4c..3a6b935 100644--- a/index.html+++ b/index.html@@ -1,4 +1,5 @@ <h1>My Diary</h1> <p>Day 1: I made a repo.</p> <p>Day 2: I learned the box.</p>-<p>TODO: write day 3</p>+<p>Day 3: I made my first commit.</p>+<p>It felt great!</p>

Plain git diff is empty now. To see what is in the box, add --staged. It compares the box with your last commit.

Watch

~/diary $ git log --onelinee1ef438 (HEAD -> main) Add day 2 entry5ba4c72 Add home page6d3a9b1 Add README~/diary $ git diff 5ba4c72 e1ef438diff --git a/index.html b/index.htmlindex 21cadf7..7420d4c 100644--- a/index.html+++ b/index.html@@ -1,3 +1,4 @@ <h1>My Diary</h1> <p>Day 1: I made a repo.</p>-<p>TODO: write day 2</p>+<p>Day 2: I learned the box.</p>+<p>TODO: write day 3</p>

You can also compare two save points. Give git diff two hashes, older first. It shows what changed between them.

Try it

Put index.html in the box. Then show the diff of the box.

Working folder

Staging area

Empty

Repository

3 save points
Add day 2 entry
Add home page
Add README

Hint

git add index.html, then git diff --staged.

You did it!

You can now spot every change before you save it.

Go deeper (optional)

--cached means the same as --staged. git diff --name-only lists only the names of changed files. Add a file name to see only that file, like git diff index.html.

~/diary $ git diff --name-onlyindex.html