Why Writing good commit messages in Git? - Purpose & Use Cases

The Big Idea

What if a few words in your commit message could save hours of frustration later?

The Scenario

Imagine you made many changes to your project and just typed random notes or left commit messages blank. Later, when you or your team try to understand what was changed or why, it feels like reading a messy diary with missing pages.

The Problem

Without clear commit messages, it becomes hard to track what each change does. This slows down fixing bugs, reviewing code, or collaborating because everyone wastes time guessing the purpose of changes.

The Solution

Writing good commit messages means giving clear, short, and meaningful descriptions for each change. This helps everyone quickly understand the history and reason behind changes, making teamwork smooth and efficient.

Before vs After

✗ Before

git commit -m "fix stuff"

✓ After

git commit -m "Fix login bug by correcting password check"

What It Enables

Clear commit messages unlock fast debugging, easy collaboration, and a clean project history everyone can trust.

Real Life Example

A developer finds a bug reported last month. Thanks to good commit messages, they quickly locate the exact change that caused it and fix it without guessing.

Key Takeaways

Good commit messages save time and reduce confusion.

They make teamwork and code reviews easier.

They create a reliable project history for the future.

Practice

1. What is the main purpose of a good commit message in Git?

easy

A. To list all files changed in the commit

B. To explain what changes were made and why

C. To include the entire code change in the message

D. To write a long story about the project history

Solution

1. Step 1: Understand the role of commit messages

   Commit messages should clearly explain what was changed and why, helping others understand the purpose.

2. Step 2: Identify the best option

   To explain what changes were made and why correctly states the purpose, while others focus on irrelevant or incorrect details.

3. Final Answer:

   To explain what changes were made and why -> Option B

4. Quick Check:

   Good commit message = explain what and why [OK]

Hint: Focus on explaining changes and reasons, not details [OK]

Common Mistakes:

• Listing files instead of explaining changes
• Writing too much unrelated history
• Including code in the message

2. Which of the following is the correct format for a good Git commit message?

easy

A. A message with only emojis

B. A long paragraph without a summary line

C. Only a list of changed files

D. A short summary line followed by a blank line and detailed explanation

Solution

1. Step 1: Recall Git commit message format

   A good commit message starts with a short summary line, then a blank line, then optional details.

2. Step 2: Match options to format

   A short summary line followed by a blank line and detailed explanation matches this format exactly; others do not follow best practices.

3. Final Answer:

   A short summary line followed by a blank line and detailed explanation -> Option D

4. Quick Check:

   Summary line + blank line + details = correct format [OK]

Hint: Use a short summary line, then details after a blank line [OK]

Common Mistakes:

• Skipping the blank line between summary and details
• Writing only a long paragraph
• Using emojis without explanation

3. Given this commit message:
Fix login bug
What is missing to make it a good commit message?

medium

A. A detailed explanation of why the bug was fixed

B. A list of all files changed

C. A longer summary line

D. The author's email

Solution

1. Step 1: Analyze the commit message content

   The message only has a short summary but lacks explanation of why the bug was fixed.

2. Step 2: Identify what improves clarity

   Adding a detailed explanation helps others understand the reason behind the fix.

3. Final Answer:

   A detailed explanation of why the bug was fixed -> Option A

4. Quick Check:

   Good message = what + why, missing why here [OK]

Hint: Add why the change was made, not just what [OK]

Common Mistakes:

• Only writing a short summary
• Listing files instead of explanation
• Adding unrelated info like author email

4. You wrote this commit message:
fix login bug
What is the main problem with this message?

medium

A. It includes a blank line after the summary

B. It is too long and detailed

C. It uses lowercase and lacks a capitalized summary

D. It uses past tense instead of present tense

Solution

1. Step 1: Check capitalization in commit messages

   Good commit messages start with a capitalized summary line.

2. Step 2: Evaluate the given message

   The message starts with lowercase 'fix', which is not recommended.

3. Final Answer:

   It uses lowercase and lacks a capitalized summary -> Option C

4. Quick Check:

   Summary line should start capitalized [OK]

Hint: Always capitalize the first letter of the summary line [OK]

Common Mistakes:

• Starting summary with lowercase letter
• Making summary too long
• Ignoring tense conventions

5. You want to write a commit message for adding a new feature that improves search speed by caching results. Which commit message is best?

hard

A. Add caching to improve search speed

Implemented a cache layer to store recent search results, reducing response time.

B. Improved search speed by adding cache

Cache added.

C. Added cache

This commit adds cache.

D. Fix search speed

Cache implemented.

Solution

1. Step 1: Evaluate clarity and detail in options

   Add caching to improve search speed Implemented a cache layer to store recent search results, reducing response time. has a clear summary and detailed explanation of what and why.

2. Step 2: Compare other options

   The other options are vague, use incorrect tense or verbs (such as 'Fix' for a new feature), or lack detailed explanation.

3. Final Answer:

   Add caching to improve search speed Implemented a cache layer to store recent search results, reducing response time. -> Option A

4. Quick Check:

   Clear summary + detailed why = best commit message [OK]

Hint: Use clear summary and explain why change matters [OK]

Common Mistakes:

• Using vague summaries
• Wrong verbs like 'Fix' for new features
• Too short or unclear explanations