git diff --staged for staged changes - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What does git diff --staged show?

You have modified a file and then added it to the staging area using git add. What will git diff --staged display?

Git

echo 'Hello' > file.txt
git add file.txt
# Now run: git diff --staged

A Shows the differences between the working directory and the last commit.

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

C Shows the differences between the working directory and the staged changes.

D Shows the differences between the staging area and the remote repository.

💡 Hint

Think about what 'staged' means in Git and what you want to compare.

git diff --staged (or git diff --cached) shows the changes that have been added to the staging area compared to the last commit. It helps you review what will be committed.

🧠 Conceptual

intermediate

Why use git diff --staged before committing?

Which reason best explains why a developer should run git diff --staged before making a commit?

A To reset the staging area to the last commit.

B To see all untracked files in the project directory.

C To compare the current branch with the remote branch.

D To verify exactly what changes are staged and will be included in the commit.

💡 Hint

Think about what you want to check before saving your changes permanently.

Running git diff --staged helps you confirm the exact changes that are staged and ready to be committed, preventing accidental commits of unwanted changes.

❓ Troubleshoot

advanced

Why does git diff --staged show no output after staging changes?

You modified a file and ran git add to stage it. But when you run git diff --staged, nothing is shown. What is the most likely reason?

A You staged the file but then modified it again without adding the new changes.

B The file was never added to the staging area.

C You are running the command in a different repository.

D The file is ignored by .gitignore.

💡 Hint

Consider whether git add actually staged any changes (e.g., no differences from HEAD or ignored file).

git diff --staged shows nothing if there are no differences between the last commit (HEAD) and the staging area. This happens if git add did not stage changes, for example if the file had no actual differences from HEAD or was ignored by .gitignore. Also, if you staged the file but then modified it again without adding the new changes, git diff --staged will show the staged version, not the working directory changes.

🔀 Workflow

advanced

Order the steps to review and commit staged changes using git diff --staged

Put these steps in the correct order to safely commit changes after staging them.

A 4,1,2,3

B 1,4,2,3

C 4,2,1,3

D 1,2,4,3

💡 Hint

Think about the natural flow from editing to committing.

You first make changes (4), then stage them (1), review staged changes (2), and finally commit (3).

✅ Best Practice

expert

Which command combination ensures you only commit staged changes and not unstaged modifications?

You have some changes staged and some unstaged. Which command sequence guarantees that only staged changes are committed?

A git commit -m 'message' && git diff --staged

B git diff --staged && git commit

C git commit -m 'message'

D git commit --only -m 'message'

💡 Hint

By default, what does git commit include?

By default, git commit commits only the staged changes. Unstaged changes remain uncommitted. The --only option is invalid and will cause an error.

Practice

1. What does the command git diff --staged show?

easy

A. Changes that are staged and ready to be committed

B. All changes in the working directory, staged or not

C. The commit history of the repository

D. Untracked files in the repository

Solution

1. Step 1: Understand what staging means in Git

   Staging means preparing changes to be saved in the next commit.

2. Step 2: Identify what git diff --staged compares

   This command compares the staged changes against the last commit, showing what will be committed.

3. Final Answer:

   Changes that are staged and ready to be committed -> Option A

4. Quick Check:

   Staged changes = git diff --staged output [OK]

Hint: Remember: --staged shows only prepared changes [OK]

Common Mistakes:

• Confusing staged changes with all changes
• Thinking it shows commit history
• Assuming it lists untracked files

2. Which of the following is the correct syntax to view staged changes using git?

easy

A. git diff staged

B. git diff --cached

C. git diff --stage

D. git diff --status

Solution

1. Step 1: Recall git diff options for staged changes

   Git uses --cached as the official option to show staged changes.

2. Step 2: Understand that --staged is an alias

   --staged is a common alias but --cached is the correct and original syntax.

3. Final Answer:

   git diff --cached -> Option B

4. Quick Check:

   Correct syntax for staged diff = git diff --cached [OK]

Hint: Use --cached to view staged changes reliably [OK]

Common Mistakes:

• Using incorrect flags like --stage
• Omitting the double dash before options
• Confusing staged with unstaged flags

3. Given the following commands executed in order:

echo 'Hello' > file.txt
git add file.txt
git diff --staged

What will git diff --staged display?

medium

A. No output, because the file is new and staged

B. An error because the file is not committed yet

C. The difference showing removal of 'Hello' in file.txt

D. The difference showing the addition of 'Hello' in file.txt

Solution

1. Step 1: Understand the state of file.txt after commands

   The file is new with content 'Hello' and has been staged with git add.

2. Step 2: What does git diff --staged show here?

   It shows the difference between the staged version and the last commit (which has no file.txt), so it shows the addition of 'Hello'.

3. Final Answer:

   The difference showing the addition of 'Hello' in file.txt -> Option D

4. Quick Check:

   New staged file diff shows added content [OK]

Hint: New staged files show additions in git diff --staged [OK]

Common Mistakes:

• Expecting no output for new files
• Thinking git diff --staged errors on new files
• Confusing removal with addition

4. You modified files in your editor, staged them with git add, ran git diff --staged but saw no output. What could be the problem?

medium

A. You staged the files but forgot to save changes in the editor

B. You used git diff instead of git diff --staged

C. You committed the changes already, so no staged changes remain

D. The repository has no commits yet

Solution

1. Step 1: Check if file changes are saved before staging

   If changes are not saved in the editor, staging old content means no visible diff.

2. Step 2: Understand why no output appears

   Since staged content matches last commit (or is empty), git diff --staged shows nothing.

3. Final Answer:

   You staged the files but forgot to save changes in the editor -> Option A

4. Quick Check:

   Unsaved edits cause empty staged diff [OK]

Hint: Always save files before staging to see diffs [OK]

Common Mistakes:

• Assuming git diff --staged shows unstaged changes
• Not realizing files were not saved
• Thinking commit status affects staged diff output

5. You have staged changes in two files: app.js and index.html. You want to see only the staged changes in app.js. Which command should you use?

hard

A. git diff --cached index.html

B. git diff app.js staged

C. git diff --staged app.js

D. git diff --staged --name-only app.js

Solution

1. Step 1: Understand how to limit git diff to a specific file

   You can specify the file path after the options to filter the diff output.

2. Step 2: Choose the correct syntax for staged changes and file filter

   git diff --staged app.js correctly shows staged changes only for app.js.

3. Final Answer:

   git diff --staged app.js -> Option C

4. Quick Check:

   File filter after --staged shows staged diff for that file [OK]

Hint: Put filename after --staged to filter staged diff [OK]

Common Mistakes:

• Placing filename before options
• Using --name-only which lists files, not diffs
• Mixing staged and unstaged file filters