Listing worktrees in Git - Time & Space Complexity

Time Complexity: Listing worktrees

O(n)

Understanding Time Complexity

When using Git, listing worktrees shows all linked working directories. Understanding how the time to list worktrees grows helps us know how fast this command runs as projects grow.

We want to know how the command's work changes as the number of worktrees increases.

Scenario Under Consideration

Analyze the time complexity of the following Git command.

git worktree list

This command lists all the worktrees linked to the current Git repository.

Identify Repeating Operations

Look for repeated steps the command does internally.

• Primary operation: Iterating over each worktree entry stored in the repository metadata.
• How many times: Once for each worktree configured (n times).

How Execution Grows With Input

The command reads and processes each worktree entry one by one.

Input Size (n)	Approx. Operations
10	10 reads and prints
100	100 reads and prints
1000	1000 reads and prints

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

Final Time Complexity

Time Complexity: O(n)

This means the time to list worktrees grows linearly with how many worktrees exist.

Common Mistake

[X] Wrong: "Listing worktrees is instant no matter how many worktrees there are."

[OK] Correct: The command must read each worktree's info, so more worktrees mean more work and time.

Interview Connect

Understanding how commands scale with input size shows you can reason about tool performance, a useful skill in real projects and interviews.

Self-Check

"What if the worktree info was cached in a single file? How would that affect the time complexity?"

Practice

1. What does the command git worktree list do?

easy

A. Deletes all existing worktrees

B. Shows the commit history of the current branch

C. Creates a new worktree

D. Shows all the linked worktrees with their paths and branches

Solution

1. Step 1: Understand the purpose of git worktree list

   This command lists all worktrees connected to the repository, showing their folder paths and branches.

2. Step 2: Compare with other options

   Options A and C describe deleting or creating worktrees, which are done by different commands. Shows the commit history of the current branch shows commit history, unrelated to worktrees.

3. Final Answer:

   Shows all the linked worktrees with their paths and branches -> Option D

4. Quick Check:

   List worktrees = B [OK]

Hint: Remember: 'list' shows all worktrees and their details [OK]

Common Mistakes:

• Confusing 'list' with 'add' or 'remove' commands
• Thinking it shows commit history
• Assuming it deletes worktrees

2. Which of the following is the correct syntax to list all git worktrees?

easy

A. git worktree show

B. git worktree ls

C. git worktree list

D. git worktree status

Solution

1. Step 1: Recall the exact command for listing worktrees

   The correct command is git worktree list to display all worktrees.

2. Step 2: Verify other options

   Options A, B, and D are invalid or do not exist in git worktree commands.

3. Final Answer:

   git worktree list -> Option C

4. Quick Check:

   Correct syntax for listing = C [OK]

Hint: Use full command 'git worktree list' to avoid errors [OK]

Common Mistakes:

• Using 'show' or 'status' instead of 'list'
• Shortening 'list' to 'ls' which is invalid
• Confusing with other git commands

3. Given the output of git worktree list below, what branch is checked out in the worktree at /projects/myrepo/feature?

/projects/myrepo  123abc [main]
/projects/myrepo/feature  456def [feature-branch]

medium

A. main

B. feature-branch

C. 123abc

D. 456def

Solution

1. Step 1: Identify the worktree path in the output

   The path /projects/myrepo/feature corresponds to the second line in the output.

2. Step 2: Read the branch name in brackets

   The branch checked out there is feature-branch, shown in square brackets.

3. Final Answer:

   feature-branch -> Option B

4. Quick Check:

   Branch at /feature = feature-branch [OK]

Hint: Branch name is always in brackets after path [OK]

Common Mistakes:

• Confusing commit hashes with branch names
• Picking the wrong line for the path
• Ignoring the brackets around branch names

4. You ran git worktree list but got an error: fatal: 'worktree' is not a git command. What is the most likely cause?

medium

A. Your git version is too old and does not support worktrees

B. You typed 'worktree' instead of 'worktrees'

C. You are not inside a git repository

D. You need to initialize worktrees with a special command first

Solution

1. Step 1: Understand the error message

   The error means git does not recognize the 'worktree' command, likely due to version.

2. Step 2: Check git version support

   Worktrees were introduced in git 2.5+. Older versions lack this command.

3. Final Answer:

   Your git version is too old and does not support worktrees -> Option A

4. Quick Check:

   Unsupported git version = A [OK]

Hint: Check git version if 'worktree' command not found [OK]

Common Mistakes:

• Assuming typo in command name
• Thinking worktrees need special init
• Not verifying git version

5. You have multiple worktrees for your project. You want to list all worktrees and filter only those on the branch named 'release'. Which command combination will achieve this?

hard

A. git worktree list | grep release

B. git worktree list --branch release

C. git worktree show release

D. git worktree list --filter=branch=release

Solution

1. Step 1: Understand git worktree list filtering options

   Git worktree list does not have built-in branch filtering options like --branch or --filter.

2. Step 2: Use shell tools to filter output

   Using grep release after listing worktrees filters lines containing 'release', showing only those branches.

3. Final Answer:

   git worktree list | grep release -> Option A

4. Quick Check:

   Filter branches by grep after list = D [OK]

Hint: Use shell grep to filter worktree list output by branch [OK]

Common Mistakes:

• Assuming git worktree list supports --branch or --filter
• Using 'show' instead of 'list'
• Expecting git to filter output internally