git diff for working directory changes - Commands & Configuration

Introduction

Sometimes you change files but haven't saved those changes to your project history yet. You need a way to see exactly what you changed before saving. The git diff command shows the differences between your current files and the last saved version.

When you want to review what you changed in a file before saving those changes.

When you accidentally modified a file and want to see what was changed.

When you want to check which lines you added or removed in your working files.

When you want to compare your current files to the last saved snapshot in git.

When you want to prepare what to save by seeing the exact changes.

Commands

This command shows the differences between your current working files and the last saved commit. It helps you see what you changed but haven't saved yet.

Terminal

git diff

Expected Output

diff --git a/example.txt b/example.txt

index e69de29..4b825dc 100644

--- a/example.txt

+++ b/example.txt

@@ -0,0 +1,2 @@

+Hello world

+This is a new line

This command shows the same differences but with colors to make added and removed lines easier to see.

Terminal

git diff --color

Expected Output

diff --git a/example.txt b/example.txt

index e69de29..4b825dc 100644

--- a/example.txt

+++ b/example.txt

@@ -0,0 +1,2 @@

+Hello world

+This is a new line

→

--color - Shows differences with color highlighting for easier reading

Key Concept

If you remember nothing else from this pattern, remember: git diff shows what you changed in your files before saving those changes.

Common Mistakes

Running git diff after saving changes with git add

git diff then shows no output because it compares working files to the last commit, but staged changes are not shown here.

Use git diff to see unstaged changes, or git diff --staged to see staged changes.

Expecting git diff to show changes for untracked new files

git diff only shows changes to files already tracked by git, not new untracked files.

Use git status to see untracked files, and git add to start tracking them.

Summary

git diff shows the changes in your working files compared to the last saved commit.

Use git diff before saving to review what you changed.

git diff does not show staged or untracked files by default.

Practice

1. What does the command git diff show you?

easy

A. The current branch name

B. The changes in your working directory that are not yet staged

C. The list of all commits in the repository

D. The status of remote branches

Solution

1. Step 1: Understand the purpose of git diff

   git diff compares your working directory files with the last saved snapshot (commit or staged changes).

2. Step 2: Identify what git diff outputs

   It shows the differences that are not yet staged for commit, meaning changes you made but haven't told git to save yet.

3. Final Answer:

   The changes in your working directory that are not yet staged -> Option B

4. Quick Check:

   git diff = unstaged changes [OK]

Hint: git diff shows unstaged file changes only [OK]

Common Mistakes:

• Confusing git diff with git status
• Thinking git diff shows committed changes
• Assuming git diff shows staged changes

2. Which of the following is the correct syntax to see changes only in a single file named app.js?

easy

A. git diff --single app.js

B. git diff --file app.js

C. git diff -f app.js

D. git diff app.js

Solution

1. Step 1: Recall the basic git diff syntax

   The command to check changes in a specific file is git diff <filename>.

2. Step 2: Match the correct option

   Only git diff app.js uses the correct syntax: git diff app.js. Other options use invalid flags.

3. Final Answer:

   git diff app.js -> Option D

4. Quick Check:

   git diff + filename = correct syntax [OK]

Hint: Use git diff followed by filename to check one file [OK]

Common Mistakes:

• Adding unsupported flags like --file or --single
• Using -f which is not for git diff
• Confusing git diff syntax with other git commands

3. Given the following scenario: You modified a file index.html by adding a new line. What will git diff index.html show?

medium

A. The difference showing the added line in index.html

B. An error saying file not found

C. No output because changes are staged

D. The full content of index.html

Solution

1. Step 1: Understand what git diff shows for a modified file

   When a file is changed but not staged, git diff filename shows the exact changes line by line.

2. Step 2: Apply this to index.html

   Since you added a line and did not stage it, the command will show the added line as a difference.

3. Final Answer:

   The difference showing the added line in index.html -> Option A

4. Quick Check:

   git diff filename = shows unstaged changes [OK]

Hint: git diff filename shows unstaged changes in that file [OK]

Common Mistakes:

• Expecting full file content instead of diff
• Thinking git diff shows staged changes
• Assuming error if file exists

4. You ran git diff but saw no output, even though you edited files. What could be the reason?

medium

A. You have untracked files only

B. You are on a detached HEAD state

C. You already staged the changes with git add

D. You have no git repository initialized

Solution

1. Step 1: Understand what git diff shows

   git diff shows changes in the working directory that are not staged.

2. Step 2: Analyze why no output appears despite edits

   If changes are already staged using git add, git diff will show nothing because working directory matches the staging area.

3. Final Answer:

   You already staged the changes with git add -> Option C

4. Quick Check:

   Staged changes hide from git diff output [OK]

Hint: No git diff output? Check if changes are staged [OK]

Common Mistakes:

• Thinking git diff shows staged changes
• Assuming untracked files appear in git diff
• Confusing detached HEAD with diff output

5. You want to review all your unstaged changes in the project but exclude changes in the docs/ folder. Which command will help you achieve this?

hard

A. git diff -- . ':!docs/'

B. git diff --exclude=docs/

C. git diff --ignore docs/

D. git diff --skip docs/

Solution

1. Step 1: Understand how to exclude paths in git diff

   Git supports pathspecs with negation using :!path syntax to exclude files or folders.

2. Step 2: Apply exclusion to docs/ folder

   The correct command uses git diff -- . ':!docs/' to show all changes except those in docs/.

3. Final Answer:

   git diff -- . ':!docs/' -> Option A

4. Quick Check:

   Use pathspec negation ':!folder/' to exclude [OK]

Hint: Use git diff with ':!folder/' to exclude paths [OK]

Common Mistakes:

• Using unsupported flags like --exclude or --ignore
• Trying --skip which is invalid
• Not using pathspec syntax for exclusion