🔍 Daily Git Workflow: Inspecting History

The Time Machine Analogy

Imagine you have a magical diary that remembers everything you ever wrote. Every word, every change, every little doodle. And the best part? You can go back and read any page from any day!

Git is like that magical diary for your code. It remembers every change you’ve ever made. Today, we’ll learn how to read this diary and discover who wrote what, when, and why.

🎯 What You’ll Learn

Think of yourself as a detective. Your job is to investigate the history of your code. You have special tools:

1. git log - Your magnifying glass to see all past entries
2. git log with filters - Your search flashlight to find specific things
3. git diff - Your comparison glasses to spot differences
4. git show - Your x-ray vision to see inside any change
5. git blame - Your truth detector to find who wrote each line

Let’s explore each one!

📖 Viewing Commit History with git log

The Story

Remember your magical diary? The git log command is like flipping through its pages from newest to oldest.

What It Shows You

Every time someone saves their work (makes a “commit”), Git writes down:

• Who made the change
• When they made it
• What they said about it (the message)
• A special code (hash) to identify it

Try It Yourself

git log

You’ll see something like:

commit a1b2c3d (HEAD -> main)
Author: Alex <alex@email.com>
Date:   Mon Nov 25 10:30:00 2024

    Add login button to homepage

commit e4f5g6h
Author: Sam <sam@email.com>
Date:   Sun Nov 24 15:45:00 2024

    Fix typo in welcome message

Making It Easier to Read

Sometimes the diary is too long! Use this shortcut:

git log --oneline

Now each entry takes just ONE line:

a1b2c3d Add login button to homepage
e4f5g6h Fix typo in welcome message
d7e8f9g Create homepage layout

Seeing the Story Flow

graph TD
    A[a1b2c3d - Add login button] --> B[e4f5g6h - Fix typo]
    B --> C[d7e8f9g - Create homepage]
    C --> D[older commits...]

🔦 Git Log Filtering

The Story

What if your diary has 1000 pages? You need a flashlight to find exactly what you’re looking for!

Find Changes by a Person

Want to see only what Alex wrote?

git log --author="Alex"

Find Changes from a Time Period

What happened last week?

git log --since="7 days ago"

What happened in November?

git log --since="2024-11-01" --until="2024-11-30"

Find Changes with Specific Words

Looking for anything about “login”?

git log --grep="login"

See Only Files That Changed

Want to know which files were touched?

git log --name-only

Combine Filters Like a Pro

git log --author="Alex" --since="1 week ago" --oneline

This shows: Alex’s changes from the past week, one per line.

Quick Reference

🔬 Comparing Changes with git diff

The Story

Imagine you have two photos of your room. One from yesterday, one from today. git diff is like a special app that shows you exactly what changed between them!

See What You Changed (But Haven’t Saved Yet)

git diff

This shows changes you made but haven’t committed yet.

What the Output Means

- old line that was removed
+ new line that was added

Red with minus (-) = This line was deleted Green with plus (+) = This line was added

Compare Two Specific Commits

git diff a1b2c3d e4f5g6h

This compares commit a1b2c3d with commit e4f5g6h.

Compare a File Between Commits

git diff a1b2c3d e4f5g6h -- style.css

Just shows changes to style.css between those commits.

See What’s Ready to Save

git diff --staged

Shows changes you’ve added (staged) but not committed yet.

Visual Understanding

graph TD
    A[Your Working Files] -->|git diff| B[Last Saved State]
    C[Commit A] -->|git diff A B| D[Commit B]
    E[Staged Changes] -->|git diff --staged| F[Last Commit]

🔎 Showing Commit Details with git show

The Story

You found an interesting page in your diary. Now you want to read EVERYTHING on that page - not just the title, but every word!

How to Use It

git show a1b2c3d

Replace a1b2c3d with any commit hash (that special code).

What You’ll See

1. The commit info (who, when, message)
2. The actual changes (what lines were added/removed)

See a Specific File in a Commit

git show a1b2c3d:index.html

This shows what index.html looked like at that exact moment in time!

See Just the Files That Changed

git show --stat a1b2c3d

Quick summary of which files changed and how much.

Example Output

commit a1b2c3d
Author: Alex <alex@email.com>
Date:   Mon Nov 25 10:30:00 2024

    Add login button to homepage

 index.html | 10 ++++++++--
 style.css  |  5 +++++
 2 files changed, 13 insertions(+), 2 deletions(-)

🕵️ Using git blame

The Story

Someone wrote a strange line of code. You’re curious: “Who wrote this? When? And why?”

git blame is like a truth detector. It tells you exactly who wrote each line!

How to Use It

git blame filename.js

What You’ll See

Every line of the file with:

• Who wrote it
• When they wrote it
• Which commit it came from

Example Output

a1b2c3d (Alex 2024-11-25) function login() {
e4f5g6h (Sam  2024-11-24)   console.log("Hello");
d7e8f9g (Alex 2024-11-23)   return true;
a1b2c3d (Alex 2024-11-25) }

Now you know:

• Alex wrote the function and the return
• Sam added the console.log

Blame a Specific Section

Only want lines 10-20?

git blame -L 10,20 filename.js

Why “Blame”?

Don’t worry! It’s not about blaming anyone. It’s about understanding who to ask when you have questions about that code.

Think of it as “git credit” - finding who deserves credit for writing each line!

🎮 Real-World Detective Story

Let’s put it all together with a story:

The Mystery: The homepage is broken. Something changed yesterday.

Your Investigation:

1. Check recent history:

   git log --since="yesterday" --oneline
   

   Found 3 commits!

2. Who made them?

   git log --since="yesterday" --format="%an - %s"
   

   Shows author names and messages.

3. What changed in index.html?

   git log -- index.html --oneline
   

   Found the suspicious commit: x1y2z3

4. See the full changes:

   git show x1y2z3
   

   Aha! Someone removed an important line!

5. Who wrote the original line?

   git blame index.html | grep "button"
   

   Mystery solved!

📝 Quick Summary

🌟 You’re Now a Git Detective!

Remember:

• git log = Your diary of all changes
• Filters = Your flashlight to find specific things
• git diff = Your comparison tool
• git show = Your deep-dive inspector
• git blame = Your truth detector

You have all the tools to investigate any mystery in your code history. Go explore!