Pull Requests and Code Review

You tested changes on your branch. Everything works! Now what?

Bad approach: Just merge to main and hope.

Professional approach: Create a Pull Request (PR) - final safety check before merging.

Time: 20 minutes

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What Is a Pull Request?

A Pull Request says: "I'm done with these changes. Please review before merging to main."

Simple flow:

Branch (your changes) → Pull Request → Review → Merge to Main

Why this matters:

• Last review chance before merging
• Shows exactly what changed (diff view)
• Documents why you made changes
• Professional workflow
• Transparent about AI assistance

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The PR Workflow

Step 1: Push Your Branch to GitHub

Get your branch from local computer to GitHub.

You ask Gemini CLI: "Push my 'add-calculator' branch to GitHub"

Gemini runs: git push -u origin add-calculator

Branch uploads to GitHub.

Check it worked: Visit your repository on GitHub - you'll see a yellow banner about recent pushes.

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Step 2: Create Pull Request on GitHub

On GitHub website:

1. Look for yellow banner: "add-calculator had recent pushes"
2. Click green "Compare & pull request" button
3. You'll see the PR creation form

OR:

1. Click "Pull requests" tab
2. Click green "New pull request" button
3. Select your branch from dropdown

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Step 3: Write PR Description

What to include:

Title (short summary):

• Example: "Add calculator module"
• Keep it 5-10 words

Description (answer 3 questions):

1. What changed?

   • List main changes
   • Be specific

2. What did AI do?

   • Document AI's role
   • Be transparent

3. How to test?

   • Give simple steps
   • Anyone should be able to verify

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Example PR description:

## What Changed
Added calculator module with 4 functions:
- add() - adds two numbers
- subtract() - subtracts two numbers
- multiply() - multiplies two numbers
- divide() - handles division by zero

## AI Assistance
- Gemini CLI generated all 4 functions
- Created unit tests (8 tests)
- Added error handling for edge cases
- Fixed bugs during testing phase

## How to Test
Run: `python test_calculator.py`
Expected: All 8 tests pass

You ask Gemini CLI: "Help me write a PR description for my calculator changes"

Gemini will generate a template based on your commits and changes.

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Step 4: Review the Diff

GitHub shows a diff (difference view):

• Green lines (+): Code added
• Red lines (-): Code removed
• Gray lines: Context (unchanged)

Check:

• Does the diff look correct?
• Any unintended changes?
• All files you meant to include?

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Step 5: Create the PR

Click "Create Pull Request" button.

PR is now live! Anyone can:

• See your changes
• Leave comments
• Approve or request changes

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Handling Feedback

Someone leaves a comment: "Add better error messages"

To update your PR:

1. Make changes locally on your branch
2. Commit the changes:

Ask Gemini CLI: "Commit my improvements with message 'Add better error messages'"

Gemini runs: git commit -m "Add better error messages"

3. Push to GitHub:

Ask Gemini CLI: "Push my updates to GitHub"

Gemini runs: git push

PR automatically updates with your new commits. No need to create a new PR.

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Merging the Pull Request

When to merge:

• All tests pass
• You've reviewed the changes
• Any feedback is addressed
• (In teams: after approval from reviewers)

On GitHub:

1. Go to your PR page
2. Click green "Merge pull request" button
3. Click "Confirm merge"

Done! Changes are now in main.

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After Merging: Clean Up

Delete the branch on GitHub:

GitHub shows "Delete branch" button after merge - click it.

Delete the branch locally:

You ask Gemini CLI: "Delete my local 'add-calculator' branch"

Gemini runs:

1. git checkout main (switch to main)
2. git pull (get the merged changes)
3. git branch -d add-calculator (delete local branch)

Your workspace is clean!

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Complete Example

You: "I finished my calculator. Write a professional PR description."

You ask Gemini CLI: "Generate a PR description for my calculator changes"

Gemini creates:

## Add Calculator Module

### Changes
- Created calculator.py with 4 operations
- Added comprehensive test suite
- Implemented error handling for division by zero

### AI Assistance
- Generated initial function implementations
- Created unit test framework
- Suggested error handling patterns
- Fixed edge case bugs

### Testing
Run: `python test_calculator.py`
All 8 tests should pass

### Files Changed
- calculator.py (new)
- test_calculator.py (new)
- README.md (updated usage instructions)

Copy this into GitHub's PR description field.

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Good vs Bad PR Descriptions

Bad ❌:

• Title: "stuff"
• Description: "added things"
• No mention of AI
• No test instructions

Good ✅:

• Title: "Add calculator module"
• Description: Lists changes, AI role, testing steps
• Clear and professional
• Anyone can understand what happened

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Key Commands Reference

Task	Command
Push branch to GitHub	git push -u origin branch-name
Push updates to PR	git push (while on branch)
Switch to main	git checkout main
Pull merged changes	git pull
Delete local branch	git branch -d branch-name
Force delete branch	git branch -D branch-name

Most PR actions happen on GitHub website (create, merge, comment).

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Safety Guidelines

Always:

• Test before creating PR
• Write clear descriptions
• Document AI assistance
• Review the diff before creating
• Clean up branches after merge

Never:

• Merge PRs with failing tests
• Leave vague descriptions
• Hide AI's role
• Merge without reviewing changes
• Keep old branches forever

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Common Mistakes

Mistake 1: Vague Titles

• Bad: "Update"
• Good: "Add calculator with 4 operations"

Mistake 2: No AI Documentation

• Bad: Silent about AI help
• Good: "AI generated functions, I tested and reviewed"

Mistake 3: Merging Too Fast

• Bad: Create PR, immediately merge (no review)
• Good: Create PR, review diff, test, then merge

Mistake 4: Not Cleaning Up

• Bad: 20 old merged branches cluttering your repo
• Good: Delete branches after merge

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Try With AI

Practice the PR workflow.

Tool: Gemini CLI (or Claude Code, ChatGPT)

Exercise 1: Create Your First PR

I have a branch "add-calculator" pushed to GitHub.
Walk me through creating a Pull Request:
1. Where do I click on GitHub?
2. What do I write in title and description?
3. How do I submit it?

Exercise 2: Write Professional Description

Generate a PR description for:
- Calculator with add, subtract, multiply, divide
- AI generated all code
- 8 tests, all passing

Make it professional but simple.

Exercise 3: Update a PR

Someone commented: "Add input validation"
Guide me through:
1. Making the changes locally
2. Committing them
3. Updating the PR on GitHub

Exercise 4: Merge and Clean Up

My PR is approved! Help me:
1. Merge it on GitHub
2. Delete the remote branch
3. Delete my local branch
4. Get the merged changes locally

Exercise 5: Review Process

Explain what happens when:
1. I push a branch to GitHub
2. I create a PR from that branch
3. I push more commits to the same branch
4. I merge the PR

Does the PR update automatically?