git diff between branches - Step-by-Step Execution

Process Flow - git diff between branches

Start: Two branches

↓

Run git diff branch1..branch2

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Git compares files

↓

Show differences line by line

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User sees changes between branches

Git compares the content of two branches and shows line-by-line differences.

Execution Sample

Git

git diff main..feature

Shows the differences between the 'main' branch and the 'feature' branch.

Process Table

Step	Command	Action	Result
1	git diff main..feature	Compare files in 'main' and 'feature'	Starts line-by-line comparison
2	git diff main..feature	Detect file changes	Finds files changed between branches
3	git diff main..feature	Show added lines (+) and removed lines (-)	Outputs diff with line markers
4	git diff main..feature	Finish comparison	All differences displayed
5	N/A	No more differences	Command ends

💡 All file differences between 'main' and 'feature' branches have been shown

Status Tracker

Variable	Start	After Step 2	After Step 3	Final
branch1	main	main	main	main
branch2	feature	feature	feature	feature
diff_output		files identified	lines with + and -	full diff text

Key Moments - 2 Insights

Why do some lines start with '+' and others with '-' in the diff output?

Lines starting with '+' are additions in the second branch, lines with '-' are removals compared to the first branch, as shown in execution_table step 3.

What does the '..' mean between branch names in the command?

The '..' tells git to compare the two branches, showing differences from the first branch to the second, as seen in execution_table step 1.

Visual Quiz - 3 Questions

Look at the execution table, what does step 3 show?

A The files that are identical

B The line-by-line differences with '+' and '-'

C The list of branches

D The commit history

💡 Hint

Refer to execution_table row 3 under 'Result' column

At which step does git finish showing all differences?

A Step 2

B Step 4

C Step 5

D Step 3

💡 Hint

Look at the 'Action' and 'Result' columns for step 5 in execution_table

If you swap the branch names in the command, how does the diff output change?

A The output shows differences from the new first branch to the second

B The output stays the same

C Git shows an error

D Git merges the branches

💡 Hint

Check variable_tracker for branch1 and branch2 roles and execution_table step 1

Concept Snapshot

git diff branch1..branch2
Shows line-by-line differences between two branches.
Lines starting with '+' are additions in branch2.
Lines starting with '-' are removals from branch1.
Use to review changes before merging.

Full Transcript

This visual execution shows how the git diff command compares two branches. First, git identifies the two branches to compare. Then it finds files that differ between them. Next, it shows the differences line by line, marking added lines with '+' and removed lines with '-'. Finally, it finishes when all differences are displayed. This helps users see what changed from one branch to another before merging or reviewing code.

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