Worktrees vs stashing decision in Git - Performance Comparison

Time Complexity: Worktrees vs stashing decision

O(n)

Understanding Time Complexity

When deciding between using git worktrees or stashing changes, it's important to understand how the time to complete these actions grows as your project size or number of changes increases.

We want to know how the effort and time scale when switching contexts with worktrees versus stashing.

Scenario Under Consideration

Analyze the time complexity of these git commands:

# Using stash
$ git stash save "WIP changes"
$ git checkout other-branch
$ git stash pop

# Using worktree
$ git worktree add ../other-branch-dir other-branch
# Work in new directory without affecting current one

This snippet shows saving changes with stash and switching branches versus creating a new worktree for parallel work.

Identify Repeating Operations

Look at what repeats or scales with input size:

• Primary operation: Saving and applying changes (stash) or creating a new worktree directory.
• How many times: Each stash save/pop involves compressing and decompressing changes; worktree creation involves linking files once.

How Execution Grows With Input

As the number of changed files or size of changes grows:

Input Size (changed files)	Approx. Operations (stash)
10	Quick compress and decompress
100	Noticeable delay saving and applying stash
1000	Longer time compressing and applying stash

Input Size (repo size)	Approx. Operations (worktree)
10 files	Quick directory setup with links
100 files	Still fast due to linking, minimal copying
1000 files	Setup time grows slowly, mostly filesystem metadata operations

Pattern observation: Stashing time grows with change size because of compression work; worktree setup grows slowly with repo size due to filesystem operations.

Final Time Complexity

Time Complexity: O(n)

This means the time to stash or create a worktree grows roughly in direct proportion to the number of changed files or repo size.

Common Mistake

[X] Wrong: "Stashing is always faster than creating a worktree regardless of project size."

[OK] Correct: Stashing involves compressing changes which can slow down as changes grow, while worktrees mostly create links and metadata, often faster for large projects.

Interview Connect

Understanding how git operations scale helps you explain your choices clearly and shows you think about efficiency, a valuable skill in real projects.

Self-Check

What if we changed from using git stash to git stash with patch mode? How would the time complexity change?

Practice

1. What is the main purpose of git stash in Git?

easy

A. Create a new branch in a separate folder

B. Temporarily save changes and clean the working directory

C. Merge two branches automatically

D. Delete untracked files from the repository

Solution

1. Step 1: Understand what git stash does

   git stash saves your current changes temporarily and cleans your working directory so you can switch branches or work on something else without committing.

2. Step 2: Compare with other options

   Creating a new branch in a separate folder is done with worktrees, not stash. Merging branches and deleting untracked files are unrelated commands.

3. Final Answer:

   Temporarily save changes and clean the working directory -> Option B

4. Quick Check:

   Stash = Temporary save changes [OK]

Hint: Stash saves changes fast, worktrees create folders [OK]

Common Mistakes:

• Confusing stash with branch creation
• Thinking stash deletes files permanently
• Mixing stash with merge operations

2. Which command correctly creates a new worktree for branch feature in folder feature-folder?

easy

A. git worktree add feature-folder feature

B. git stash create feature-folder feature

C. git branch add feature-folder feature

D. git checkout -b feature feature-folder

Solution

1. Step 1: Recall the syntax for adding a worktree

   The correct syntax is git worktree add <path> <branch>. So git worktree add feature-folder feature creates a new folder with the branch checked out.

2. Step 2: Check other options for correctness

   git stash create is invalid for this purpose. git branch add is not a valid command. git checkout -b creates a branch but does not create a separate folder.

3. Final Answer:

   git worktree add feature-folder feature -> Option A

4. Quick Check:

   Worktree add = git worktree add [OK]

Hint: Worktree add uses: git worktree add folder branch [OK]

Common Mistakes:

• Using stash commands to create worktrees
• Confusing branch creation with worktree creation
• Incorrect order of arguments in commands

3. You have uncommitted changes on branch main. You want to switch to feature branch without losing changes. What happens if you run git stash then git checkout feature?

medium

A. Git throws an error and refuses to switch branches

B. Changes are lost permanently after checkout

C. Changes are saved temporarily, branch switches cleanly

D. Changes are automatically merged into feature branch

Solution

1. Step 1: Understand what git stash does before switching

   git stash saves your uncommitted changes safely and cleans your working directory so you can switch branches without conflicts.

2. Step 2: Effect of git checkout feature after stash

   Since the working directory is clean after stash, Git switches to feature branch without errors or losing changes. You can later apply the stash.

3. Final Answer:

   Changes are saved temporarily, branch switches cleanly -> Option C

4. Quick Check:

   Stash saves changes, checkout switches branch [OK]

Hint: Stash before checkout saves changes safely [OK]

Common Mistakes:

• Assuming changes are lost after stash
• Expecting automatic merge of stashed changes
• Thinking Git errors on switching with stash

4. You tried to create a worktree with git worktree add feature but got an error. What is the most likely cause?

medium

A. The folder name is missing, causing a syntax error

B. You have uncommitted changes that block worktree creation

C. The branch feature does not exist

D. You forgot to stash changes before adding worktree

Solution

1. Step 1: Check the command syntax

   git worktree add requires two arguments: folder path and branch name. The command git worktree add feature only has one argument, so it is missing the folder name.

2. Step 2: Understand error cause

   Missing folder argument causes Git to throw a syntax error. Uncommitted changes or branch existence issues cause different errors, but syntax error is most likely here.

3. Final Answer:

   The folder name is missing, causing a syntax error -> Option A

4. Quick Check:

   Worktree add needs folder and branch [OK]

Hint: Worktree add needs folder then branch [OK]

Common Mistakes:

• Ignoring missing folder argument
• Assuming uncommitted changes block worktree add
• Confusing stash necessity with worktree creation

5. You want to work on two branches, main and feature, simultaneously without committing unfinished work on main. Which approach is best?

hard

A. Use git stash to save changes on main and switch branches repeatedly

B. Delete the feature branch and work only on main

C. Commit unfinished work on main before switching to feature

D. Create a worktree for feature branch to work in a separate folder

Solution

1. Step 1: Understand the need for parallel work

   You want to work on two branches at the same time without committing unfinished work on main. Stashing and switching repeatedly is slow and error-prone.

2. Step 2: Choose the best tool for parallel branch work

   Worktrees allow you to have multiple branches checked out in different folders simultaneously. This lets you work on main and feature side by side without switching or stashing.

3. Final Answer:

   Create a worktree for feature branch to work in a separate folder -> Option D

4. Quick Check:

   Worktrees = parallel branches in folders [OK]

Hint: Worktrees let you work on branches side-by-side [OK]

Common Mistakes:

• Using stash repeatedly instead of worktrees
• Committing unfinished work prematurely
• Deleting needed branches accidentally