git log formatting options - Time & Space Complexity

Time Complexity: git log formatting options

O(n)

Understanding Time Complexity

We want to understand how the time to run git log with formatting options changes as the number of commits grows.

How does adding more commits affect the work done when formatting the log output?

Scenario Under Consideration

Analyze the time complexity of the following git command.

git log --pretty=format:"%h - %an, %ar : %s"

This command lists commit history with a custom format showing short hash, author name, relative date, and commit message.

Identify Repeating Operations

Look for repeated actions in the command.

• Primary operation: Formatting each commit's data into the specified string.
• How many times: Once for every commit in the history being shown.

How Execution Grows With Input

As the number of commits increases, the command formats each commit one by one.

Input Size (n)	Approx. Operations
10	10 formatting operations
100	100 formatting operations
1000	1000 formatting operations

Pattern observation: The work grows directly with the number of commits; doubling commits doubles the work.

Final Time Complexity

Time Complexity: O(n)

This means the time to format the log grows linearly with the number of commits shown.

Common Mistake

[X] Wrong: "Formatting the log output is instant no matter how many commits there are."

[OK] Correct: Each commit must be processed and formatted, so more commits mean more work and more time.

Interview Connect

Understanding how commands scale with input size helps you write efficient scripts and troubleshoot performance in real projects.

Self-Check

"What if we add a filter to show only commits by one author? How would the time complexity change?"

Practice

1. What does the %h placeholder represent in git log --pretty=format:"%h %s"?

easy

A. Author name

B. Abbreviated commit hash

C. Commit date

D. Full commit message

Solution

1. Step 1: Understand %h in git log format

   The placeholder %h stands for the abbreviated commit hash, a short version of the commit ID.

2. Step 2: Compare with other placeholders

   %an is author name, %cd is commit date, and %s is the commit message. So %h is unique for the commit hash.

3. Final Answer:

   Abbreviated commit hash -> Option B

4. Quick Check:

   Commit hash short form [OK]

Hint: Remember: %h = short hash, %an = author name [OK]

Common Mistakes:

• Confusing %h with %an (author name)
• Thinking %h shows full commit message
• Mixing %h with commit date placeholder

2. Which of the following is the correct syntax to show the author name followed by commit message using git log --pretty=format?

easy

A. git log --pretty=format:"%an %s"

B. git log --pretty=format:"%s %an"

C. git log --pretty=format:"%author %message"

D. git log --pretty=format:"%name %subject"

Solution

1. Step 1: Identify correct placeholders for author and message

   The correct placeholders are %an for author name and %s for commit message.

2. Step 2: Check syntax correctness

   git log --pretty=format:"%an %s" uses %an %s which is valid. Options A and C use invalid placeholders. git log --pretty=format:"%s %an" reverses order but is still valid syntax, but question asks for author then message.

3. Final Answer:

   git log --pretty=format:"%an %s" -> Option A

4. Quick Check:

   Author then message [OK]

Hint: Use %an for author, %s for message in format string [OK]

Common Mistakes:

• Using invalid placeholders like %author or %message
• Swapping order when question specifies author first
• Missing quotes around format string

3. What will be the output of this command if the latest commit hash is abc1234, author is Jane, and message is Fix bug?

git log -1 --pretty=format:"%h - %an: %s"

medium

A. Fix bug - Jane: abc1234

B. abc1234 Jane Fix bug

C. Jane - abc1234: Fix bug

D. abc1234 - Jane: Fix bug

Solution

1. Step 1: Understand placeholders in format string

   The format string is %h - %an: %s. %h is abbreviated hash, %an is author name, %s is commit message.

2. Step 2: Substitute given values

   Replacing placeholders: %h = abc1234, %an = Jane, %s = Fix bug. So output is "abc1234 - Jane: Fix bug".

3. Final Answer:

   abc1234 - Jane: Fix bug -> Option D

4. Quick Check:

   Format placeholders replaced correctly [OK]

Hint: Match placeholders to values exactly in order [OK]

Common Mistakes:

• Mixing order of placeholders and values
• Ignoring separators like '-' and ':'
• Confusing full hash with abbreviated hash

4. You run git log --pretty=format:"%h %an %msg" but get an error. What is the problem?

medium

A. The placeholder %msg is invalid

B. Missing quotes around format string

C. Using %h and %an together is not allowed

D. Command needs --oneline option

Solution

1. Step 1: Identify invalid placeholder

   The placeholder %msg does not exist in git log formatting. The correct placeholder for commit message is %s.

2. Step 2: Check other parts of command

   Quotes are present, and using %h and %an together is valid. The --oneline option is optional and unrelated to this error.

3. Final Answer:

   The placeholder %msg is invalid -> Option A

4. Quick Check:

   Invalid placeholder causes error [OK]

Hint: Use %s for message, not %msg [OK]

Common Mistakes:

• Typing %msg instead of %s
• Forgetting quotes around format string
• Assuming --oneline is required for formatting

5. You want to list commits showing only the abbreviated hash, author email, and commit date in ISO format. Which command achieves this?

hard

A. git log --pretty=format:"%h %an %cd" --date=short

B. git log --pretty=format:"%H %ae %cd" --date=iso

C. git log --pretty=format:"%h %ae %cd" --date=iso

D. git log --pretty=format:"%h %ae %cd" --date=relative

Solution

1. Step 1: Identify placeholders for required info

   %h is abbreviated hash, %ae is author email, %cd is commit date.

2. Step 2: Choose correct date format option

   --date=iso shows date in ISO 8601 format, which matches requirement.

3. Step 3: Verify options

   git log --pretty=format:"%h %ae %cd" --date=iso matches all requirements. git log --pretty=format:"%h %an %cd" --date=short uses %an (author name) and short date, not email or ISO. git log --pretty=format:"%H %ae %cd" --date=iso uses %H (full hash), not abbreviated. git log --pretty=format:"%h %ae %cd" --date=relative uses relative date format, not ISO.

4. Final Answer:

   git log --pretty=format:"%h %ae %cd" --date=iso -> Option C

5. Quick Check:

   Abbreviated hash, email, ISO date [OK]

Hint: Use %ae for email and --date=iso for ISO date format [OK]

Common Mistakes:

• Using %an instead of %ae for email
• Choosing wrong date format option
• Using full hash %H instead of abbreviated %h