git diff --staged for staged changes - Step-by-Step Execution

Process Flow - git diff --staged for staged changes

Make changes to files

↓

Stage changes with git add

↓

Run git diff --staged

↓

Show differences between staged files and last commit

↓

Use output to review staged changes

This flow shows how you first modify files, then stage them, and finally use 'git diff --staged' to see what changes are ready to be committed.

Execution Sample

Git

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

This sequence creates or modifies file.txt, stages it, then shows the staged changes compared to the last commit.

Process Table

Step	Command	Action	Output/Result
1	echo 'Hello' > file.txt	Create or overwrite file.txt with 'Hello'	file.txt content: Hello
2	git add file.txt	Stage file.txt changes	file.txt is now in staging area
3	git diff --staged	Show differences between staged file.txt and last commit	--- a/file.txt +++ b/file.txt @@ -0,0 +1 @@ +Hello
4	End	No more commands	Ready to commit staged changes

💡 After step 3, all staged changes are shown; no unstaged changes appear.

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3
file.txt content	empty or previous content	Hello	Hello (staged)	Hello (staged)
Staging area	empty	empty	file.txt staged	file.txt staged

Key Moments - 2 Insights

Why does 'git diff --staged' show changes only after staging?

'git diff --staged' compares the staging area to the last commit, so only files added with 'git add' appear in its output, as shown in step 3 of the execution table.

What if I modify a file but don't stage it, will 'git diff --staged' show it?

No, unstaged changes are not shown by 'git diff --staged'. Only staged changes appear, as the command compares staged files to the last commit.

Visual Quiz - 3 Questions

Look at the execution table, what does 'git diff --staged' output at step 3?

A The differences between the working directory and the last commit

B The differences between the staged file and the last commit

C A list of all files in the repository

D The commit history

💡 Hint

Check the 'Output/Result' column at step 3 in the execution table.

At which step does the file get added to the staging area?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look at the 'Action' column to see when 'git add' is run.

If you modify file.txt again after step 2 but do not stage it, what will 'git diff --staged' show?

A It will show the staged version only

B It will show the new modifications

C It will show no differences

D It will show an error

💡 Hint

Refer to the key moment explaining what 'git diff --staged' compares.

Concept Snapshot

git diff --staged shows differences between staged files and last commit.
Use 'git add' to stage changes first.
It helps review what will be committed.
Unstaged changes are not shown.
Useful for confirming staged content before commit.

Full Transcript

This visual execution shows how to use 'git diff --staged' to see staged changes. First, you modify or create a file. Then you stage it with 'git add'. Running 'git diff --staged' compares the staged file to the last commit and shows the differences. Unstaged changes do not appear in this output. This helps you review exactly what changes are ready to be committed.

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