Stashing specific files in Git - Time & Space Complexity

Time Complexity: Stashing specific files

O(n)

Understanding Time Complexity

When using git to stash specific files, it's important to understand how the time to stash grows as the number of files changes.

We want to know how the work git does changes when you stash more or fewer files.

Scenario Under Consideration

Analyze the time complexity of the following git commands.

git stash push path/to/file1 path/to/file2
# or equivalently
git stash push -- path/to/file1 path/to/file2

This command stashes changes only in the specified files, not all changes in the repository.

Identify Repeating Operations

• Primary operation: Git scans and processes each specified file's changes.
• How many times: Once per specified file, so the number of files given.

How Execution Grows With Input

As you stash more files, git does more work linearly with the number of files.

Input Size (n)	Approx. Operations
10 files	Processes changes in 10 files
100 files	Processes changes in 100 files
1000 files	Processes changes in 1000 files

Pattern observation: The work grows directly with the number of files you stash.

Final Time Complexity

Time Complexity: O(n)

This means the time to stash grows in a straight line as you add more files to stash.

Common Mistake

[X] Wrong: "Stashing specific files takes the same time no matter how many files I include."

[OK] Correct: Git must check and save changes for each file you list, so more files mean more work and more time.

Interview Connect

Understanding how git handles specific files helps you explain efficiency in version control tasks, a useful skill in real projects.

Self-Check

"What if you stash all changes without specifying files? How would the time complexity change?"

Practice

1. What does the command git stash push -m "save changes" file.txt do?

easy

A. It saves changes only from file.txt to a new stash with a message.

B. It saves all changes in the working directory to a stash with a message.

C. It commits file.txt with the message "save changes".

D. It deletes file.txt and saves the rest to stash.

Solution

1. Step 1: Understand the git stash push command

   This command saves changes in the working directory to a stash instead of committing.

2. Step 2: Recognize the effect of specifying a file

   By adding file.txt, only changes in that file are saved to the stash, not all files.

3. Final Answer:

   It saves changes only from file.txt to a new stash with a message. -> Option A

4. Quick Check:

   Stash specific file = It saves changes only from file.txt to a new stash with a message. [OK]

Hint: Use git stash push with file names to stash specific files [OK]

Common Mistakes:

• Thinking it stashes all files without specifying
• Confusing stash with commit
• Assuming it deletes files

2. Which of the following is the correct syntax to stash only -index.html and style.css files?

easy

A. git stash push -- -index.html style.css

B. git stash push -- files -index.html style.css

C. git stash push -index.html style.css

D. git stash push -f -index.html style.css

Solution

1. Step 1: Recall the syntax for stashing specific files

   The correct syntax uses git stash push -- <files> to specify files.

2. Step 2: Identify the correct option

   git stash push -- -index.html style.css uses -- before file names, which is required to separate options from file paths.

3. Final Answer:

   git stash push -- -index.html style.css -> Option A

4. Quick Check:

   Use -- before files to stash specific files [OK]

Hint: Always use -- before file names in stash command [OK]

Common Mistakes:

• Omitting -- before file names
• Using unsupported flags like -f
• Adding extra words like 'files'

3. Given these changes:
-file1.txt modified, file2.txt modified, file3.txt unchanged.
What will be the output of git stash push -- -file1.txt followed by git stash list?

medium

A. Shows an error because multiple files are modified.

B. Shows a stash with -file1.txt and file2.txt changes saved.

C. Shows a stash with only -file1.txt changes saved.

D. Shows no stash because file2.txt is not included.

Solution

1. Step 1: Understand what git stash push -- -file1.txt does

   This command saves only changes from -file1.txt to a new stash.

2. Step 2: Check the stash list output

   After stashing, git stash list shows the new stash entry with only -file1.txt changes saved.

3. Final Answer:

   Shows a stash with only -file1.txt changes saved. -> Option C

4. Quick Check:

   Stash specific file = stash list shows that file only [OK]

Hint: Stash command saves only specified files, stash list shows saved entries [OK]

Common Mistakes:

• Assuming all modified files are stashed
• Expecting an error when multiple files are modified
• Confusing stash list output with file contents

4. You run git stash push -file1.txt but get an error: error: unknown option '-file1.txt'. What is the likely cause?

medium

A. You used the wrong command; git stash save is required.

B. The file -file1.txt does not exist.

C. You need to commit changes before stashing.

D. You forgot to add -- before the file name.

Solution

1. Step 1: Analyze the error message

   The error says unknown option '-file1.txt', meaning Git treats the file name as an option.

2. Step 2: Identify correct syntax for stashing specific files

   You must use -- before file names to separate options from file paths.

3. Final Answer:

   You forgot to add -- before the file name. -> Option D

4. Quick Check:

   Missing -- causes unknown option error [OK]

Hint: Add -- before files to avoid option parsing errors [OK]

Common Mistakes:

• Omitting -- before file names
• Assuming file must be committed first
• Using deprecated stash commands

5. You have modified -app.js, index.html, and style.css. You want to stash only -app.js and style.css, then later apply those changes back. Which sequence of commands correctly does this?

hard

A. git stash push -app.js style.cssgit stash apply

B. git stash push -m "partial stash" -- -app.js style.cssgit stash apply stash@{0}

C. git stash save -app.js style.cssgit stash pop

D. git stash push -app.js style.cssgit stash pop stash@{1}

Solution

1. Step 1: Stash specific files with a message

   Use git stash push -m "partial stash" -- -app.js style.css to stash only selected files with a label.

2. Step 2: Apply the correct stash entry

   Use git stash apply stash@{0} to apply the most recent stash explicitly.

3. Final Answer:

   git stash push -m "partial stash" -- -app.js style.css
   git stash apply stash@{0} -> Option B

4. Quick Check:

   Use -m and -- with files, then apply stash by name [OK]

Hint: Use -m for message and -- before files, then apply stash by reference [OK]

Common Mistakes:

• Using deprecated git stash save
• Omitting -- before file names
• Applying stash without specifying correct stash reference