git diff between branches - Commands & Configuration

Introduction

Sometimes you want to see what changes exist between two versions of your project. Git diff between branches helps you compare the differences in files and code between two branches so you know what changed.

When you want to review code changes before merging one branch into another

When you want to understand what updates a teammate made on their branch

When you want to check if your feature branch has new changes compared to the main branch

When you want to find out what files were added, removed, or modified between branches

When you want to prepare a summary of changes for a code review or deployment

Commands

This command shows the differences between the 'main' branch and the 'feature-branch'. It lists all changes in files line by line so you can see what was added or removed.

Terminal

git diff main feature-branch

Expected Output

diff --git a/app.js b/app.js

index e69de29..d95f3ad 100644

--- a/app.js

+++ b/app.js

@@ -0,0 +1,5 @@

+console.log('New feature added');

+function greet() {

+  return 'Hello!';

+}

+

This command lists only the names of files that differ between the 'main' and 'feature-branch'. It helps you quickly see which files changed without showing the details.

Terminal

git diff --name-only main feature-branch

Expected Output

app.js

index.html

styles.css

→

--name-only - Show only the names of changed files, not the content differences

This command shows a summary of changes between the branches, including how many lines were added or removed in each file. It gives a quick overview of the size of changes.

Terminal

git diff --stat main feature-branch

Expected Output

 app.js      | 5 +++++

 index.html  | 2 ++

 styles.css  | 3 +++

 3 files changed, 10 insertions(+)

→

--stat - Show a summary of changes with line counts per file

Key Concept

If you remember nothing else from this pattern, remember: git diff between branches lets you see exactly what changed in files before merging or deploying.

Common Mistakes

Running 'git diff' without specifying both branch names

This shows changes only between your current branch and the working directory, not between two branches.

Always specify both branches like 'git diff main feature-branch' to compare them directly.

Using branch names that do not exist or are misspelled

Git will show an error because it cannot find the branches to compare.

Check branch names with 'git branch' and type them exactly as shown.

Summary

Use 'git diff branch1 branch2' to see detailed line-by-line changes between two branches.

Use 'git diff --name-only branch1 branch2' to list only the files that changed.

Use 'git diff --stat branch1 branch2' to get a summary of how many lines changed per file.

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