git stash apply vs pop - Performance Comparison

Time Complexity: git stash apply vs pop

O(n)

Understanding Time Complexity

When using git stash, it's important to know how the commands apply and pop behave in terms of work done as stash size grows.

We want to understand how the time to run these commands changes as the stash content grows.

Scenario Under Consideration

Analyze the time complexity of these git commands:

git stash apply stash@{0}
git stash pop stash@{0}

These commands restore changes saved in the stash. apply restores but keeps the stash, pop restores and removes it.

Identify Repeating Operations

Look at what happens internally when these commands run.

• Primary operation: Applying the saved changes (patch) to the current working directory.
• How many times: The patch is applied once per command execution, regardless of stash size.

How Execution Grows With Input

The time to apply or pop depends on the size of the changes saved in the stash, not the number of stashes.

Input Size (lines changed)	Approx. Operations
10	Small patch applied quickly
100	More lines to apply, takes longer
1000	Large patch, noticeably slower

Pattern observation: Time grows roughly in proportion to the size of the changes being applied.

Final Time Complexity

Time Complexity: O(n)

This means the time to apply or pop grows linearly with the size of the changes in the stash.

Common Mistake

[X] Wrong: "Applying or popping a stash takes longer if I have many stashes saved."

[OK] Correct: The number of stashes does not affect the time; only the size of the changes in the stash being applied matters.

Interview Connect

Understanding how git commands scale with input size helps you reason about performance in real projects, showing you can think about efficiency beyond just writing code.

Self-Check

What if we changed from applying a single stash to applying multiple stashes one after another? How would the time complexity change?

Practice

1. What is the main difference between git stash apply and git stash pop?

easy

A. git stash apply only shows the stash content, git stash pop applies it.

B. git stash apply deletes the stash after applying, git stash pop keeps it.

C. git stash apply restores changes but keeps the stash saved, while git stash pop restores changes and removes the stash.

D. git stash apply creates a new stash, git stash pop deletes all stashes.

Solution

1. Step 1: Understand git stash apply behavior

   This command restores the saved changes from the stash but keeps the stash entry intact for future use.

2. Step 2: Understand git stash pop behavior

   This command restores the changes and then removes the stash entry, cleaning up automatically.

3. Final Answer:

   git stash apply restores changes but keeps the stash saved, while git stash pop restores changes and removes the stash. -> Option C

4. Quick Check:

   Apply keeps stash, pop removes stash [OK]

Hint: Apply keeps stash, pop removes stash after applying [OK]

Common Mistakes:

• Thinking apply deletes stash
• Confusing pop with apply
• Believing apply only previews changes
• Assuming pop keeps stash

2. Which of the following is the correct syntax to restore stash changes and remove the stash entry?

easy

A. git stash apply

B. git stash pop

C. git stash save

D. git stash list

Solution

1. Step 1: Identify command to restore and remove stash

   git stash pop restores the changes and deletes the stash entry.

2. Step 2: Confirm other commands

   git stash apply restores but keeps stash; git stash save creates stash; git stash list shows stashes.

3. Final Answer:

   git stash pop -> Option B

4. Quick Check:

   Pop restores and removes stash [OK]

Hint: Pop restores and deletes stash, apply keeps stash [OK]

Common Mistakes:

• Using apply instead of pop to remove stash
• Confusing save with pop
• Trying to remove stash with list
• Using wrong command syntax

3. Given this sequence of commands:

git stash save "work in progress"
git stash apply

What happens to the stash list after these commands?

medium

A. The stash list still contains the saved stash.

B. The stash list is empty.

C. The stash list contains two identical stashes.

D. The stash list is deleted.

Solution

1. Step 1: Save a stash

   git stash save "work in progress" creates a stash entry and saves changes.

2. Step 2: Apply stash without removing

   git stash apply restores changes but keeps the stash entry intact.

3. Final Answer:

   The stash list still contains the saved stash. -> Option A

4. Quick Check:

   Apply keeps stash in list [OK]

Hint: Apply restores but stash remains in list [OK]

Common Mistakes:

• Assuming apply removes stash
• Thinking stash list duplicates
• Believing stash list clears automatically
• Confusing apply with pop

4. You ran git stash pop but got a conflict error. What should you do to fix this?

medium

A. Run git stash apply again to fix conflicts automatically.

B. Run git stash pop again without resolving conflicts.

C. Delete the stash file manually from .git folder.

D. Manually resolve conflicts, then run git stash drop to remove stash.

Solution

1. Step 1: Understand conflict on pop

   git stash pop applies changes and removes stash, but conflicts can occur if changes clash.

2. Step 2: Resolve conflicts and clean stash

   Manually fix conflicts, then remove stash with git stash drop if pop did not remove it due to conflict.

3. Final Answer:

   Manually resolve conflicts, then run git stash drop to remove stash. -> Option D

4. Quick Check:

   Fix conflicts, then drop stash manually [OK]

Hint: Resolve conflicts manually, then drop stash [OK]

Common Mistakes:

• Rerunning pop without fixing conflicts
• Assuming apply fixes conflicts automatically
• Deleting stash files manually
• Ignoring conflicts and continuing

5. You want to test changes saved in a stash without removing it, then later clean up if everything works. Which sequence of commands should you use?

hard

A. git stash apply; if okay, git stash drop

B. git stash pop; if okay, git stash apply

C. git stash drop; then git stash apply

D. git stash list; git stash pop

Solution

1. Step 1: Use git stash apply to test changes

   This command restores changes but keeps stash, so you can test without losing the stash.

2. Step 2: Remove stash if tests pass

   If changes work well, run git stash drop to delete the stash and clean up.

3. Final Answer:

   git stash apply; if okay, git stash drop -> Option A

4. Quick Check:

   Apply to test, drop to clean [OK]

Hint: Apply to test, drop to remove stash later [OK]

Common Mistakes:

• Using pop first and losing stash before testing
• Dropping stash before applying
• Applying stash twice unnecessarily
• Confusing list with apply or pop