Pull request process in Git - Time & Space Complexity

Time Complexity: Pull request process

O(n)

Understanding Time Complexity

We want to understand how the time needed for a pull request process changes as the project grows.

Specifically, how does the number of changes affect the work done during a pull request?

Scenario Under Consideration

Analyze the time complexity of this simplified pull request workflow.

# Fetch latest changes
git fetch origin

# Create a new branch
git checkout -b feature-branch

# Make changes and commit
# (assume multiple commits)

# Push branch to remote
git push origin feature-branch

# Open pull request on platform
# Review and merge
    

This snippet shows the main steps to create and submit a pull request for review and merging.

Identify Repeating Operations

Look for repeated actions or loops in this process.

• Primary operation: Reviewing each commit and changed file in the pull request.
• How many times: Once per changed file or commit, depending on review depth.

How Execution Grows With Input

As the number of changed files or commits grows, the review work grows too.

Input Size (changed files)	Approx. Operations (review steps)
10	10 review steps
100	100 review steps
1000	1000 review steps

Pattern observation: The review effort grows roughly in direct proportion to the number of changes.

Final Time Complexity

Time Complexity: O(n)

This means the time to complete a pull request grows linearly with the number of changes to review.

Common Mistake

[X] Wrong: "The pull request time stays the same no matter how many files are changed."

[OK] Correct: More changes mean more code to read and check, so it takes more time.

Interview Connect

Understanding this helps you explain how code review scales and why small, focused pull requests are easier to manage.

Self-Check

"What if the pull request includes automated tests that run on each commit? How would the time complexity change?"

Practice

1. What is the main purpose of a pull request in Git?

easy

A. To ask your team to review and merge your code changes

B. To delete a branch from the repository

C. To create a new branch locally

D. To clone a repository to your computer

Solution

1. Step 1: Understand the role of a pull request

   A pull request is a request to merge code changes and get feedback from the team.

2. Step 2: Identify the correct purpose

   Options B, C, and D describe other Git actions unrelated to pull requests.

3. Final Answer:

   To ask your team to review and merge your code changes -> Option A

4. Quick Check:

   Pull request = code review request [OK]

Hint: Pull request means asking for code review and merge [OK]

Common Mistakes:

• Confusing pull request with branch creation
• Thinking pull request deletes branches
• Mixing pull request with cloning repositories

2. Which Git command is used to upload your local branch to the remote repository before creating a pull request?

easy

A. git clone origin branch-name

B. git pull origin branch-name

C. git push origin branch-name

D. git fetch origin branch-name

Solution

1. Step 1: Identify the command to upload local changes

   The git push command sends local commits to the remote repository.

2. Step 2: Match the correct syntax

   git push origin branch-name uploads the specified branch to the remote named origin.

3. Final Answer:

   git push origin branch-name -> Option C

4. Quick Check:

   Push = upload branch to remote [OK]

Hint: Push uploads your branch to remote before pull request [OK]

Common Mistakes:

• Using git clone instead of git push
• Confusing git pull with git push
• Using git fetch which only downloads data

3. After pushing your branch and creating a pull request, what is the expected output when you run git status on your local branch?

medium

A. On branch feature-xyz
nothing to commit, working tree clean

B. On branch feature-xyz
your branch is ahead of 'origin/feature-xyz' by 1 commit

C. On branch main
nothing to commit, working tree clean

D. On branch feature-xyz
You have unmerged paths.

Solution

1. Step 1: Understand the state after pushing and creating pull request

   After pushing, local and remote branches are synced, so no new commits locally.

2. Step 2: Interpret git status output

   "nothing to commit, working tree clean" means no changes locally; branch is up to date.

3. Final Answer:

   On branch feature-xyz nothing to commit, working tree clean -> Option A

4. Quick Check:

   Clean status means local branch matches remote [OK]

Hint: Clean git status means branch is synced after push [OK]

Common Mistakes:

• Thinking branch is ahead after push
• Confusing branch names
• Expecting unmerged paths without conflicts

4. You created a pull request but forgot to push your latest commit. What error will you most likely see when trying to create the pull request?

medium

A. Pull request created successfully with all commits

B. Error: No commits found on branch to compare

C. Merge conflict detected automatically

D. Remote branch does not exist

Solution

1. Step 1: Understand the pull request creation process

   A pull request compares your remote branch with the base branch.

2. Step 2: Identify the error when branch is not pushed

   If you forget to push, the remote branch does not exist, causing an error.

3. Final Answer:

   Remote branch does not exist -> Option D

4. Quick Check:

   Pull request needs remote branch [OK]

Hint: Push branch first or remote branch won't exist [OK]

Common Mistakes:

• Assuming pull request works without pushing
• Expecting merge conflict before push
• Ignoring remote branch creation step

5. You want to ensure your pull request is merged only after at least two team members approve it. Which GitHub feature should you configure?

hard

A. Enable auto-merge without reviews

B. Branch protection rules with required reviews set to 2

C. Use git rebase to combine commits

D. Create a new branch for each reviewer

Solution

1. Step 1: Identify how to enforce review requirements

   GitHub branch protection rules allow setting required number of reviewers before merge.

2. Step 2: Match the feature to the requirement

   Setting required reviews to 2 ensures at least two approvals before merging.

3. Final Answer:

   Branch protection rules with required reviews set to 2 -> Option B

4. Quick Check:

   Branch protection = enforce review count [OK]

Hint: Use branch protection rules to require reviews [OK]

Common Mistakes:

• Confusing auto-merge with review enforcement
• Thinking git rebase controls reviews
• Creating branches per reviewer is unnecessary