Git mental model (snapshots not diffs) - Commands & Configuration

Introduction

Git saves your project by taking snapshots of all files at each save point, not by saving only the changes. This helps you see the whole project state at any time easily.

When you want to save your work safely and be able to go back to any previous version.

When you want to share your project with others and track all changes clearly.

When you want to understand how your project looked at a specific moment in time.

When you want to avoid losing work by saving snapshots often.

When you want to compare different versions of your project easily.

Commands

This command creates a new Git repository in your current folder so Git can start tracking snapshots of your project.

Terminal

git init

Expected Output

Initialized empty Git repository in /your/path/.git/

This command tells Git to prepare all current files for the next snapshot. It stages the files so they will be included in the next commit.

Terminal

git add .

Expected Output

No output (command runs silently)

This command takes a snapshot of all staged files and saves it with a message describing the snapshot.

Terminal

git commit -m "Initial snapshot"

Expected Output

[master (root-commit) abcdef1] Initial snapshot

 3 files changed, 30 insertions(+)

 create mode 100644 file1.txt

 create mode 100644 file2.txt

 create mode 100644 file3.txt

→

-m - Adds a message describing the snapshot

This command shows a list of all snapshots taken so far, with their short IDs and messages.

Terminal

git log --oneline

Expected Output

abcdef1 Initial snapshot

Key Concept

If you remember nothing else from this pattern, remember: Git saves your project by taking full snapshots of all files at each commit, not just the changes.

Common Mistakes

Trying to commit without adding files first

Git only saves files that have been staged with 'git add', so the commit will be empty if you skip this step.

Always run 'git add' on the files you want to include before committing.

Thinking Git saves only file differences

Git actually saves snapshots of the entire project state, which helps it restore any version quickly and reliably.

Understand that each commit is a snapshot of all files, so you can see the whole project at that point.

Summary

Initialize a Git repository with 'git init' to start tracking snapshots.

Use 'git add' to stage files you want to include in the next snapshot.

Run 'git commit -m "message"' to save a snapshot with a description.

Use 'git log --oneline' to see all saved snapshots and their messages.

Practice

1. What does Git save when you run git commit?

easy

A. A backup copy of your entire computer

B. Only the changes made since the last commit

C. A list of all commands you typed

D. A snapshot of all your files at that moment

Solution

1. Step 1: Understand what git commit does

   It records the current state of your project files as a snapshot.

2. Step 2: Differentiate snapshot from changes

   Unlike some systems, Git saves the whole snapshot, not just the changes.

3. Final Answer:

   A snapshot of all your files at that moment -> Option D

4. Quick Check:

   Git saves snapshots, not diffs [OK]

Hint: Remember: Git snapshots whole files, not just changes [OK]

Common Mistakes:

• Thinking Git saves only changes (diffs)
• Confusing commit with backup
• Believing commit saves command history

2. Which of the following is the correct command to create a snapshot in Git?

easy

A. git snapshot

B. git save

C. git commit

D. git backup

Solution

1. Step 1: Recall Git commands for saving work

   The command to save a snapshot is git commit.

2. Step 2: Verify other options

   Commands like git snapshot, git save, and git backup do not exist in Git.

3. Final Answer:

   git commit -> Option C

4. Quick Check:

   git commit creates snapshots [OK]

Hint: Use git commit to save snapshots [OK]

Common Mistakes:

• Using non-existent commands like git save
• Confusing commit with backup commands
• Trying git snapshot which is invalid

3. Given this sequence of commands:

echo "Hello" > file.txt
git add file.txt
git commit -m "First snapshot"
echo "World" >> file.txt
git add file.txt
git commit -m "Second snapshot"

What does the second commit snapshot contain?

medium

A. Only the line "World" added to file.txt

B. The entire file.txt with both "Hello" and "World" lines

C. Only the line "Hello" in file.txt

D. An empty file.txt

Solution

1. Step 1: Understand what each commit saves

   Each commit saves a full snapshot of the file at that time, not just changes.

2. Step 2: Analyze the second commit content

   After appending "World", the second commit snapshot includes both "Hello" and "World" lines in file.txt.

3. Final Answer:

   The entire file.txt with both "Hello" and "World" lines -> Option B

4. Quick Check:

   Git snapshots save full file content [OK]

Hint: Each commit saves full file content, not just added lines [OK]

Common Mistakes:

• Thinking commit saves only new lines
• Confusing snapshots with diffs
• Assuming commit saves partial file

4. You ran git commit but Git says "nothing to commit, working tree clean". What is the most likely reason?

medium

A. There are no changes since the last snapshot

B. You forgot to add files with git add before commit

C. Your Git repository is corrupted

D. You need to restart your computer

Solution

1. Step 1: Understand the message meaning

   "Nothing to commit, working tree clean" means no changes are detected compared to last commit.

2. Step 2: Check if files were changed

   If no files changed, Git has no new snapshot to save, so commit does nothing.

3. Final Answer:

   There are no changes since the last snapshot -> Option A

4. Quick Check:

   No changes = no new snapshot [OK]

Hint: No changes means no new commit possible [OK]

Common Mistakes:

• Assuming you must always run git add before commit even if no changes
• Thinking repository is corrupted
• Restarting computer unnecessarily

5. You want to save your project state but only some files changed. How does Git store this when you run git commit?

hard

A. Git saves a full snapshot of all files, but reuses unchanged files from previous commits internally

B. Git saves only the changed files as diffs

C. Git saves only the changed files as full copies

D. Git saves nothing until you run git push

Solution

1. Step 1: Recall Git snapshot model

   Git saves a full snapshot of the project at commit time, not just diffs.

2. Step 2: Understand Git's storage optimization

   Internally, Git reuses unchanged files from previous commits to save space efficiently.

3. Final Answer:

   Git saves a full snapshot of all files, but reuses unchanged files from previous commits internally -> Option A

4. Quick Check:

   Snapshots with internal reuse = Git saves a full snapshot of all files, but reuses unchanged files from previous commits internally [OK]

Hint: Git snapshots all files but stores unchanged ones efficiently [OK]

Common Mistakes:

• Thinking Git saves only diffs
• Believing commit saves nothing until push
• Assuming changed files are saved as full copies only