git diff between branches - Mini Project: Build & Apply

Compare Changes Between Git Branches Using git diff

📖 Scenario: You are working on a software project using Git. You have two branches: main and feature. You want to see what changes have been made in the feature branch compared to main before merging.

🎯 Goal: Learn how to use the git diff command to compare differences between two branches.

📋 What You'll Learn

Have a Git repository with two branches named main and feature

Use git diff to compare branches

Understand how to specify branch names in git diff

💡 Why This Matters

🌍 Real World

Developers often work on separate branches to add features or fix bugs. Comparing branches helps review what changes will be merged.

💼 Career

Knowing how to compare branches with <code>git diff</code> is essential for code reviews and collaboration in software development teams.

1

Create two branches main and feature

Create a Git branch called main and another branch called feature.

Git

# Create branch main
# Create branch feature

Hint

Use git branch branch_name to create a branch.

2

Add a file and commit changes on main branch

Switch to the main branch, create a file named app.txt with the text Main branch content, add it to Git, and commit with the message Initial commit on main.

Git

git branch main
git branch feature
# Switch to main branch
# Create app.txt with content
# Add and commit changes

Hint

Use git checkout main to switch branches. Use echo to create file content.

3

Make a change on the feature branch

Switch to the feature branch, modify app.txt by adding the line Feature branch addition, add and commit the change with the message Update on feature branch.

Git

git branch main
git branch feature
git checkout main
echo "Main branch content" > app.txt
git add app.txt
git commit -m "Initial commit on main"
# Switch to feature branch
# Append text to app.txt
# Add and commit changes

Hint

Use git checkout feature to switch branches. Use >> to append text to a file.

4

Use git diff to compare feature branch with main

Run the command git diff main..feature to see the changes made in the feature branch compared to main.

Git

git branch main
git branch feature
git checkout main
echo "Main branch content" > app.txt
git add app.txt
git commit -m "Initial commit on main"
git checkout feature
echo "Feature branch addition" >> app.txt
git add app.txt
git commit -m "Update on feature branch"
# Run git diff to compare main and feature branches

Hint

Use git diff main..feature to compare the two branches.

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