git diff between branches - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of git diff between two branches

What will be the output of the following command if branch feature has 3 new lines added to app.py compared to main?

Git

git diff main..feature -- app.py

A Shows the commit history of <code>feature</code> branch

B Shows all files changed between <code>main</code> and <code>feature</code> including <code>app.py</code>

C Shows no output because <code>git diff</code> does not compare branches

D Shows the 3 new lines added in <code>app.py</code> compared to <code>main</code>

💡 Hint

Use git diff branch1..branch2 to see differences between branches.

The command git diff main..feature -- app.py shows the changes in app.py that exist in feature but not in main. It only shows the diff for that file.

🧠 Conceptual

intermediate

Understanding git diff branch range syntax

Which of the following correctly describes what git diff branchA..branchB shows?

A All commits that exist in both branches

B Changes needed to convert <code>branchB</code> into <code>branchA</code>

C Changes needed to convert <code>branchA</code> into <code>branchB</code>

D The list of files changed in <code>branchA</code> only

💡 Hint

Think about which branch is the base and which is the target.

git diff branchA..branchB shows the changes that would transform branchA into branchB. It compares the tips of the two branches.

❓ Troubleshoot

advanced

Why does git diff show no output between branches?

You run git diff main..feature but see no output, even though you expect differences. What could be a reason?

A Both branches point to the same commit, so no differences exist

B You forgot to add files to the staging area

C The command only shows differences in the working directory, not between branches

D You need to run <code>git fetch</code> before <code>git diff</code>

💡 Hint

Check if the branches have diverged commits.

If both branches point to the same commit, there are no differences to show, so git diff outputs nothing.

🔀 Workflow

advanced

Using git diff to review changes before merging

You want to review all changes in branch feature compared to main before merging. Which command is best?

A git diff main..feature

B git diff feature..main

C git merge feature

D git log main..feature

💡 Hint

Think about which branch is the base and which is the feature.

git diff main..feature shows all changes in feature that are not in main. This helps review before merging.

✅ Best Practice

expert

Best practice for comparing branches with uncommitted changes

You have uncommitted changes in your working directory. You want to compare feature branch with main. What is the best practice?

A Stash or commit your changes before running <code>git diff main..feature</code>

B Run <code>git diff main..feature</code> directly; uncommitted changes do not affect it

C Use <code>git diff --cached main..feature</code> to ignore uncommitted changes

D Reset your working directory to discard uncommitted changes before diff

💡 Hint

git diff between branches compares branch tips and ignores working directory.

git diff main..feature compares the trees at the tips of the branches, unaffected by uncommitted changes in the working directory or index.

Practice

1. What does the command git diff branch1 branch2 show you?

easy

A. The commit history of branch1

B. The list of branches in the repository

C. The differences in code between branch1 and branch2

D. The status of files in the current branch

Solution

1. Step 1: Understand the purpose of git diff

   The git diff command compares changes between two points in Git, such as branches.

2. Step 2: Identify what comparing two branches means

   Comparing branch1 and branch2 shows the code differences between them.

3. Final Answer:

   The differences in code between branch1 and branch2 -> Option C

4. Quick Check:

   git diff branch1 branch2 = code differences [OK]

Hint: git diff between branches shows code changes [OK]

Common Mistakes:

• Thinking it shows commit history
• Confusing with git branch command
• Expecting file status instead of differences

2. Which of the following is the correct syntax to see differences between two branches named main and feature?

easy

A. git diff main feature

B. git diff --branches main feature

C. git diff feature..main

D. git diff main..feature

Solution

1. Step 1: Recall git diff syntax for branches

   The basic syntax is git diff branch1 branch2 without dots or extra flags.

2. Step 2: Evaluate each option

   git diff main feature uses git diff main feature, which is correct. Options A and C use double dots which is incorrect for git diff. git diff --branches main feature uses a non-existent flag.

3. Final Answer:

   git diff main feature -> Option A

4. Quick Check:

   Correct syntax = git diff main feature [OK]

Hint: Use 'git diff branch1 branch2' without dots [OK]

Common Mistakes:

• Using double dots '..' with git diff
• Adding unsupported flags like --branches
• Swapping branch order without reason

3. Given two branches, main and dev, where dev has added a new line console.log('Hello'); in app.js, what will git diff main dev show?

medium

A. An error message about branch names

B. A line removed: -console.log('Hello');

C. No output because branches are the same

D. A line added: +console.log('Hello');

Solution

1. Step 1: Understand what git diff shows for added lines

   When a line is added in the second branch, git diff shows it with a plus sign (+).

2. Step 2: Apply to the example

   The new line console.log('Hello'); added in dev will appear as a line starting with + in the diff output.

3. Final Answer:

   A line added: +console.log('Hello'); -> Option D

4. Quick Check:

   Added lines show with + in git diff [OK]

Hint: Added lines show with + in git diff output [OK]

Common Mistakes:

• Thinking added lines show with -
• Expecting no output for changes
• Confusing branch order in diff

4. You run git diff main feature but get no output even though you know feature has changes. What is a likely reason?

medium

A. You forgot to commit changes in feature branch

B. The branches have no differences

C. You are currently on the feature branch

D. You used the wrong command syntax

Solution

1. Step 1: Understand git diff compares committed changes

   Git diff between branches compares committed differences, not uncommitted changes.

2. Step 2: Identify why no output appears

   If changes are not committed in feature, git diff won't show them when comparing branches.

3. Final Answer:

   You forgot to commit changes in feature branch -> Option A

4. Quick Check:

   Uncommitted changes not shown in branch diff [OK]

Hint: Only committed changes appear in git diff between branches [OK]

Common Mistakes:

• Expecting uncommitted changes to show
• Confusing current branch with diff branches
• Assuming syntax error without checking commits

5. You want to review all changes between release and hotfix branches but only for files in the src/ folder. Which command correctly shows this?

hard

A. git diff release..hotfix src/

B. git diff release hotfix -- src/

C. git diff --src release hotfix

D. git diff release hotfix --path src/

Solution

1. Step 1: Understand how to limit git diff to a folder

   Git diff allows specifying paths after a double dash -- to limit output to those files or folders.

2. Step 2: Check each option for correct syntax

   git diff release hotfix -- src/ uses git diff release hotfix -- src/, which correctly limits diff to src/. git diff release..hotfix src/ uses double dots incorrectly. Options C and D use invalid flags.

3. Final Answer:

   git diff release hotfix -- src/ -> Option B

4. Quick Check:

   Use -- then folder to limit git diff [OK]

Hint: Use -- then folder path to filter git diff output [OK]

Common Mistakes:

• Using double dots '..' with git diff
• Adding unsupported flags like --src or --path
• Placing folder path before branch names