git stash to save changes - Time & Space Complexity

Time Complexity: git stash to save changes

O(n)

Understanding Time Complexity

We want to understand how the time to save changes with git stash grows as the number of changed files increases.

How does the command handle more changes and how long does it take?

Scenario Under Consideration

Analyze the time complexity of the following git commands.

git stash save "work in progress"
git stash list
git stash apply stash@{0}

This snippet saves current changes to a stash, lists all stashes, and applies the latest stash.

Identify Repeating Operations

Look for operations that repeat or scale with input size.

• Primary operation: Saving changes involves scanning all changed files and storing their state.
• How many times: The operation touches each changed file once during stash save.

How Execution Grows With Input

As the number of changed files grows, the time to save them grows roughly in direct proportion.

Input Size (changed files)	Approx. Operations
10	10 file scans and saves
100	100 file scans and saves
1000	1000 file scans and saves

Pattern observation: The time grows linearly as more files are changed.

Final Time Complexity

Time Complexity: O(n)

This means the time to stash changes grows directly with the number of changed files.

Common Mistake

[X] Wrong: "Stashing changes takes the same time no matter how many files are changed."

[OK] Correct: The command must process each changed file, so more files mean more work and more time.

Interview Connect

Understanding how commands scale with input size shows you can think about efficiency in real tools, a useful skill for any DevOps role.

Self-Check

"What if we stash only specific files instead of all changes? How would the time complexity change?"

Practice

1. What does the git stash command do?

easy

A. Commits your changes permanently to the repository

B. Deletes all your untracked files

C. Temporarily saves your uncommitted changes to switch tasks

D. Creates a new branch from the current state

Solution

1. Step 1: Understand the purpose of git stash

   The command saves your current uncommitted changes temporarily without committing them.

2. Step 2: Compare with other git commands

   Unlike commit, stash does not save changes permanently; it allows switching tasks without losing work.

3. Final Answer:

   Temporarily saves your uncommitted changes to switch tasks -> Option C

4. Quick Check:

   git stash = temporary save [OK]

Hint: Stash saves changes temporarily without committing [OK]

Common Mistakes:

• Thinking stash commits changes permanently
• Confusing stash with branch creation
• Assuming stash deletes files

2. Which of the following is the correct command to save your current changes using git stash?

easy

A. git stash add

B. git stash save

C. git stash commit

D. git stash push

Solution

1. Step 1: Identify the modern git stash command

   The recommended command to save changes is git stash push, which explicitly pushes changes to the stash.

2. Step 2: Eliminate incorrect options

   git stash save is deprecated, git stash commit and git stash add are invalid commands.

3. Final Answer:

   git stash push -> Option D

4. Quick Check:

   Use git stash push to save changes [OK]

Hint: Use 'git stash push' to save changes safely [OK]

Common Mistakes:

• Using deprecated 'git stash save'
• Trying 'git stash commit' which doesn't exist
• Confusing stash with add or commit commands

3. Given the following commands run in sequence:

git stash push -m "work in progress"
git stash list
git stash apply

What will be the output of git stash list?

medium

A. No stash entries found.

B. stash@{0}: On main: work in progress

C. Error: stash not found

D. stash@{1}: On main: work in progress

Solution

1. Step 1: Understand the effect of git stash push -m "work in progress"

   This command saves current changes with the message "work in progress" as the latest stash entry.

2. Step 2: Check git stash list output

   Since this is the first stash, it appears as stash@{0}: On main: work in progress.

3. Final Answer:

   stash@{0}: On main: work in progress -> Option B

4. Quick Check:

   First stash is stash@{0} with message [OK]

Hint: First stash is always stash@{0} in the list [OK]

Common Mistakes:

• Expecting no stash entries after push
• Confusing stash@{0} with stash@{1}
• Assuming apply removes stash entry

4. You ran git stash push but accidentally included untracked files. Which command fixes this by stashing only tracked files?

medium

A. git stash push --keep-index

B. git stash push --only-tracked

C. git stash push --no-untracked

D. git stash push --include-untracked

Solution

1. Step 1: Understand the problem with untracked files

   By default, git stash push does not stash untracked files unless specified.

2. Step 2: Identify the correct option to stash only tracked files

   --keep-index stashes changes but keeps the index intact, effectively ignoring untracked files.

3. Final Answer:

   git stash push --keep-index -> Option A

4. Quick Check:

   Use --keep-index to stash only tracked files [OK]

Hint: Use --keep-index to exclude untracked files from stash [OK]

Common Mistakes:

• Using --include-untracked adds untracked files instead of excluding
• Assuming --no-untracked or --only-tracked are valid options
• Confusing stash options with git add options

5. You have two stashes saved:

stash@{0}: On main: fix bug
stash@{1}: On main: add feature

You want to apply the older stash (add feature) but keep both stashes after applying. Which command should you use?

hard

A. git stash apply stash@{1}

B. git stash pop stash@{1}

C. git stash drop stash@{1}

D. git stash branch stash@{1}

Solution

1. Step 1: Understand difference between apply and pop

   git stash apply applies the stash but keeps it saved; git stash pop applies and removes it.

2. Step 2: Choose command to apply older stash without removing it

   Use git stash apply stash@{1} to apply the older stash and keep both stashes intact.

3. Final Answer:

   git stash apply stash@{1} -> Option A

4. Quick Check:

   Apply keeps stash, pop removes stash [OK]

Hint: Use 'git stash apply' to keep stash after applying [OK]

Common Mistakes:

• Using pop removes stash entry
• Dropping stash deletes it without applying
• Confusing branch command with apply