Look back in time

Your diary title now says “My Git Diary”. When did that change? And what did the page look like before?

~/diary $ git log --oneline78933de (HEAD -> main) Change title to My Git Diaryd57aaf3 Add day 3 entrybc602fc Add day 2 entryabc5111 Add day 1 entry7d2fe9d Add home page

git log --oneline puts each commit on one line: short hash, then message. The newest is on top.

Slide back to the very first commit. Watch index.html change.

index.html<h1>My Git Diary</h1><p>Day 1: I made a repo.</p><p>Day 2: I learned the box.</p><p>Day 3: I made my first commit.</p>

~/diary $ git log --oneline --graph --all* 78933de (HEAD -> main) Change title to My Git Diary* d57aaf3 Add day 3 entry* bc602fc Add day 2 entry* abc5111 Add day 1 entry* 7d2fe9d Add home page

--graph draws your timeline with stars and lines. --all adds every branchbranch: A storyline of commits. Each branch has a name, like main.. You have just one, so it is a straight line.

~/diary $ git show bc602fccommit bc602fc6482595a6cb712215e1edd2a6963b2effAuthor: You <you@example.com>Date:   Fri Oct 30 09:03:00 2026 +0800    Add day 2 entrydiff --git a/index.html b/index.htmlindex 5a63042..98811d7 100644--- a/index.html+++ b/index.html@@ -1,2 +1,3 @@ <h1>My Diary</h1> <p>Day 1: I made a repo.</p>+<p>Day 2: I learned the box.</p>

git show plus a hash opens one commit: who, when, and exactly what changed. Green + lines were added.

Find the hash of “Add day 2 entry”. Then open it with git show.

You want to see exactly what one commit changed. Which command?

You can now travel back through your history and see every change.