Handling PR feedback and updates in Git - Time & Space Complexity

Time Complexity: Handling PR feedback and updates

O(n)

Understanding Time Complexity

When working with pull requests (PRs), we often update code based on feedback. Understanding how the time to apply these updates grows helps us manage our work efficiently.

We want to know: how does the effort to update a PR change as the number of feedback points or changes grows?

Scenario Under Consideration

Analyze the time complexity of the following git commands used to update a PR after feedback.

git checkout feature-branch
# Make code changes based on feedback
git add .
git commit -m "Address PR feedback"
git push origin feature-branch

This snippet shows the typical steps to update a feature branch with new changes after receiving PR feedback.

Identify Repeating Operations

Look for repeated actions that affect time.

• Primary operation: Adding and committing changed files.
• How many times: Once per update cycle, but the number of files changed can vary.

How Execution Grows With Input

As the number of files or lines changed grows, the time to stage and commit grows roughly in proportion.

Input Size (changed files)	Approx. Operations
10	10 file adds + 1 commit
100	100 file adds + 1 commit
1000	1000 file adds + 1 commit

Pattern observation: The time grows linearly with the number of changed files because each file must be added before committing.

Final Time Complexity

Time Complexity: O(n)

This means the time to update a PR grows in direct proportion to the number of files or changes you need to stage and commit.

Common Mistake

[X] Wrong: "Updating a PR takes the same time no matter how many files I change."

[OK] Correct: Each changed file must be added and committed, so more changes mean more work and more time.

Interview Connect

Understanding how your work scales with the size of changes shows you can manage code updates efficiently. This skill helps you plan and communicate better in real projects.

Self-Check

"What if instead of adding all files at once, you add files one by one in a loop? How would the time complexity change?"

Practice

1. When you receive feedback on a pull request (PR), what is the first step to update your code accordingly?

easy

A. Check out the feature branch locally to make changes

B. Merge the main branch into your feature branch without changes

C. Close the PR and create a new one

D. Delete the feature branch and start over

Solution

1. Step 1: Switch to the feature branch

   You need to work on the branch where the PR was created to apply feedback changes.

2. Step 2: Make the necessary code updates

   After switching, edit the code to address the feedback.

3. Final Answer:

   Check out the feature branch locally to make changes -> Option A

4. Quick Check:

   Update code on feature branch = A [OK]

Hint: Always update code on the feature branch first [OK]

Common Mistakes:

• Trying to update main branch instead of feature branch
• Closing PR unnecessarily
• Starting a new branch without reason

2. Which git command correctly stages all changed files before committing updates for a PR?

easy

A. git commit -a -m "Update code"

B. git checkout -b update-branch

C. git push origin main

D. git add .

Solution

1. Step 1: Stage all changes

   The command git add . stages all modified and new files in the current directory.

2. Step 2: Commit the staged changes

   After staging, you use git commit -m "message" to save changes locally.

3. Final Answer:

   git add . -> Option D

4. Quick Check:

   Stage all changes = git add . [OK]

Hint: Use 'git add .' to stage all changes before commit [OK]

Common Mistakes:

• Using git commit -a without staging new files
• Pushing before committing
• Creating new branches unnecessarily

3. Given the following commands run in sequence on a feature branch:

git add file.txt
git commit -m "Fix typo"
git push origin feature-branch

What happens to the existing pull request linked to feature-branch?

medium

A. A new pull request is created

B. The pull request updates automatically with the new commit

C. The pull request is closed

D. Nothing changes until you merge manually

Solution

1. Step 1: Push updates to the feature branch

   Pushing commits to the branch linked to the PR updates the PR automatically.

2. Step 2: PR reflects new commits

   The PR shows the new changes for reviewers to see and re-review.

3. Final Answer:

   The pull request updates automatically with the new commit -> Option B

4. Quick Check:

   Push to feature branch updates PR = A [OK]

Hint: Push changes to update existing PR automatically [OK]

Common Mistakes:

• Thinking a new PR is needed for each update
• Believing PR closes on push
• Assuming manual merge needed to update PR

4. You tried to push updates to your feature branch but got this error:
! [rejected] feature-branch -> feature-branch (non-fast-forward)
What is the best way to fix this?

medium

A. Pull latest changes from remote and rebase before pushing

B. Delete the remote branch and push again

C. Force push with git push --force

D. Create a new branch and push there

Solution

1. Step 1: Fetch and rebase remote changes

   Run git pull --rebase origin feature-branch to update your local branch with remote changes without merge commits.

2. Step 2: Push the rebased branch

   After rebasing, push your changes normally with git push origin feature-branch.

3. Final Answer:

   Pull latest changes from remote and rebase before pushing -> Option A

4. Quick Check:

   Fix non-fast-forward by rebasing and pushing = C [OK]

Hint: Rebase remote changes before pushing to avoid errors [OK]

Common Mistakes:

• Using force push without caution
• Deleting remote branch unnecessarily
• Creating new branches instead of syncing

5. You have multiple commits in your feature branch but want to combine them into one clean commit before updating the PR. Which sequence of commands achieves this?

hard

A. git merge main; git commit -m "Clean update"; git push

B. git rebase -i main; edit commits; git push

C. git reset --soft HEAD~3; git commit -m "Clean update"; git push --force

D. git checkout main; git cherry-pick feature-branch; git push

Solution

1. Step 1: Soft reset last 3 commits

   git reset --soft HEAD~3 moves HEAD back but keeps changes staged, allowing to combine commits.

2. Step 2: Create a single new commit and force push

   Commit staged changes with a new message, then force push to update PR with one clean commit.

3. Final Answer:

   git reset --soft HEAD~3; git commit -m "Clean update"; git push --force -> Option C

4. Quick Check:

   Combine commits by soft reset and force push = B [OK]

Hint: Use soft reset and force push to squash commits [OK]

Common Mistakes:

• Using merge instead of squash
• Forgetting to force push after rewriting history
• Incorrectly rebasing without editing commits