git diff for working directory changes - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of git diff after modifying a tracked file?

You have a file app.txt tracked by Git. You change a line in this file but do not stage it. What does git diff show?

Git

git diff

A Shows the line differences between the last committed version and the current modified file.

B Shows the differences between the staged changes and the last commit.

C Shows no output because changes are not staged.

D Shows the commit history of the file.

💡 Hint

Think about what git diff compares by default when no options are given.

git diff by default shows changes in the working directory compared to the index (staging area). Since the file is modified but not staged, it shows the differences between the index and the current file.

🧠 Conceptual

intermediate

Which command shows differences between staged changes and the last commit?

You have modified and staged some files. You want to see what changes are staged compared to the last commit. Which command do you use?

A git diff --cached

B git diff --staged

C Both B and C

D git diff

💡 Hint

There are two equivalent options to show staged changes.

git diff --staged and git diff --cached both show differences between the index (staged files) and the last commit.

❓ Troubleshoot

advanced

Why does git diff show no output after modifying a file?

You edited a tracked file but running git diff shows no output. What could be the reason?

A You have no changes in the working directory.

B The file was staged already, so changes are not in working directory.

C The file is ignored by Git.

D You ran <code>git diff</code> in a different directory.

💡 Hint

Think about what git diff compares by default.

If the file is staged, git diff shows differences between working directory and index. If no changes exist in working directory (because changes are staged), it shows nothing.

🔀 Workflow

advanced

What is the correct sequence to view unstaged changes, stage them, and then view staged changes?

Arrange these commands in the correct order to see unstaged changes, stage them, and then see staged changes.

A 2, 1, 3

B 1, 2, 3

C 3, 2, 1

D 2, 3, 1

💡 Hint

First see unstaged changes, then stage, then see staged changes.

First, git diff shows unstaged changes. Then git add stages them. Finally, git diff --staged shows staged changes.

✅ Best Practice

expert

Which command safely shows all changes including untracked files before committing?

You want to review all changes including unstaged, staged, and untracked files before committing. Which command shows this best?

A git diff

B git diff --name-only

C git diff HEAD

D git status

💡 Hint

Think about which command summarizes all changes and untracked files.

git status shows staged, unstaged changes and untracked files in a clear summary, helping review before commit.

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