Fork and pull request workflow in Git - Time & Space Complexity

Time Complexity: Fork and pull request workflow

O(n)

Understanding Time Complexity

We want to understand how the time needed grows when using the fork and pull request workflow in git.

Specifically, how the number of steps changes as the project or contributions grow.

Scenario Under Consideration

Analyze the time complexity of the following git commands in a fork and pull request workflow.

# Fork the repository on GitHub
# Clone your fork locally
$ git clone https://github.com/yourname/project.git

# Create a new branch for your feature
$ git checkout -b feature-branch

# Make changes and commit
$ git add .
$ git commit -m "Add feature"

# Push branch to your fork
$ git push origin feature-branch

# Open a pull request on GitHub

This sequence shows the main steps a contributor takes to add changes via a fork and pull request.

Identify Repeating Operations

Look for repeated actions or loops in the workflow.

• Primary operation: Making and committing changes locally (git add and git commit).
• How many times: This depends on how many changes or features the contributor works on; each change involves these steps.

How Execution Grows With Input

As the number of changes or features (n) increases, the number of commits and pushes also increases roughly linearly.

Input Size (n)	Approx. Operations
10 changes	About 10 commits and pushes
100 changes	About 100 commits and pushes
1000 changes	About 1000 commits and pushes

Pattern observation: The time grows roughly in direct proportion to the number of changes made.

Final Time Complexity

Time Complexity: O(n)

This means the time needed grows linearly with the number of changes you want to contribute.

Common Mistake

[X] Wrong: "Pushing one big commit is faster than many small commits in terms of workflow time complexity."

[OK] Correct: While fewer commits mean fewer pushes, making many small commits helps track changes better and does not reduce the overall linear growth of work steps.

Interview Connect

Understanding how your work scales in a fork and pull request workflow shows you can manage contributions efficiently as projects grow.

Self-Check

"What if you worked directly on the main repository instead of a fork? How would the time complexity change?"

Practice

1. What is the main purpose of forking a repository in the fork and pull request workflow?

easy

A. To clone the repository locally without any changes

B. To delete the original project

C. To create a personal copy of the project to work on independently

D. To merge changes directly into the original repository

Solution

1. Step 1: Understand the concept of forking

   Forking creates a personal copy of the original project on your GitHub account, allowing you to work independently without affecting the original.

2. Step 2: Identify the purpose in the workflow

   This personal copy lets you safely make changes and experiment before proposing them back to the original project.

3. Final Answer:

   To create a personal copy of the project to work on independently -> Option C

4. Quick Check:

   Fork = personal copy for safe work [OK]

Hint: Fork means copy project to your account for safe changes [OK]

Common Mistakes:

• Confusing fork with clone
• Thinking fork deletes original
• Assuming fork merges changes automatically

2. Which command correctly pushes a new branch named feature1 to your forked repository?

easy

A. git push origin main

B. git push upstream feature1

C. git push fork feature1

D. git push origin feature1

Solution

1. Step 1: Identify the remote name for your fork

   By default, your fork is set as the remote named origin. The original repository is usually upstream.

2. Step 2: Use the correct push syntax

   To push a branch named feature1 to your fork, use git push origin feature1.

3. Final Answer:

   git push origin feature1 -> Option D

4. Quick Check:

   Push branch to origin (your fork) = git push origin branch [OK]

Hint: Push new branch to origin, not upstream [OK]

Common Mistakes:

• Using upstream instead of origin for push
• Pushing main branch instead of feature branch
• Using incorrect remote name like fork

3. After forking a repo and pushing a branch fix-bug to your fork, what is the next step to propose your changes to the original project?

medium

A. Directly push fix-bug branch to the original repository

B. Create a pull request from your fork's fix-bug branch to the original repo

C. Merge fix-bug branch locally without pushing

D. Delete your fork and clone the original repo again

Solution

1. Step 1: Understand the pull request purpose

   A pull request asks the original project to review and merge your changes from your fork's branch.

2. Step 2: Identify the correct action after pushing

   After pushing your branch to your fork, you create a pull request targeting the original repository's branch.

3. Final Answer:

   Create a pull request from your fork's fix-bug branch to the original repo -> Option B

4. Quick Check:

   Push branch then create pull request [OK]

Hint: Push branch, then open pull request to original repo [OK]

Common Mistakes:

• Trying to push directly to original repo without permission
• Merging locally without sharing changes
• Deleting fork before proposing changes

4. You forked a repo and created a branch update-docs. You pushed it but forgot to sync your fork with the original repo first. What problem might occur when creating a pull request?

medium

A. Merge conflicts due to outdated fork base

B. Your pull request will be automatically merged

C. Your branch will be deleted automatically

D. No changes will be visible in the pull request

Solution

1. Step 1: Understand syncing forks

   If your fork is behind the original repo, your branch may not include recent changes from the original.

2. Step 2: Identify the pull request impact

   This can cause merge conflicts when the original repo tries to merge your changes because the base is outdated.

3. Final Answer:

   Merge conflicts due to outdated fork base -> Option A

4. Quick Check:

   Outdated fork causes merge conflicts [OK]

Hint: Always sync fork before starting new branch [OK]

Common Mistakes:

• Assuming pull request merges automatically
• Thinking branch deletes itself
• Believing changes won't show without sync

5. You forked a project and created two branches: featureA and featureB. You pushed both branches to your fork. How do you create pull requests so the original repo can review and merge these features independently?

hard

A. Create separate pull requests for each branch targeting the original repo's main branch

B. Create one pull request combining both branches

C. Push both branches to upstream and wait for automatic merge

D. Merge featureB into featureA locally, then create a single pull request

Solution

1. Step 1: Understand pull request scope

   Each pull request represents changes from one branch to the original repo, allowing independent review.

2. Step 2: Apply to multiple branches

   To keep features separate, create one pull request per branch targeting the original repo's main branch.

3. Final Answer:

   Create separate pull requests for each branch targeting the original repo's main branch -> Option A

4. Quick Check:

   One pull request per branch for independent review [OK]

Hint: Make one pull request per branch for clear reviews [OK]

Common Mistakes:

• Combining branches in one pull request
• Pushing branches directly to upstream without PR
• Merging branches locally before PR