feat: add module 9 for cherry picking

2026-01-04 17:29:52 +01:00
parent 23f0ff511c
commit 8f488c2e88
4 changed files with 596 additions and 0 deletions
--- a/module-09-cherry-pick/README.md
+++ b/module-09-cherry-pick/README.md
@@ -0,0 +1,160 @@
+# Module 09: Cherry-Pick
+
+## Learning Objectives
+
+By the end of this module, you will:
+- Understand what cherry-picking is and how it works
+- Know when to use cherry-pick vs merge or rebase
+- Apply specific commits from one branch to another
+- Handle cherry-pick conflicts if they occur
+- Understand common use cases for cherry-picking
+
+## Challenge Description
+
+You have a `development` branch with several commits. Some of these commits are bug fixes that need to be applied to the `main` branch immediately, but other commits are experimental features that shouldn't be merged yet.
+
+Your task is to:
+1. Review the commits on the development branch
+2. Identify which commits are bug fixes
+3. Cherry-pick only the bug fix commits to the main branch
+4. Verify that main has the bug fixes but not the experimental features
+
+## Key Concepts
+
+### What is Cherry-Pick?
+
+Cherry-pick allows you to apply a specific commit from one branch to another. Instead of merging an entire branch, you can selectively choose individual commits.
+
+```
+    A---B---C---D development
+   /
+  E---F main
+```
+
+After cherry-picking commit C:
+```
+    A---B---C---D development
+   /
+  E---F---C' main
+```
+
+Note that C' is a new commit with the same changes as C but a different commit hash.
+
+### Cherry-Pick vs Merge vs Rebase
+
+- **Merge**: Brings all commits from another branch and creates a merge commit
+- **Rebase**: Replays all commits from your branch on top of another branch
+- **Cherry-Pick**: Applies one or more specific commits to your current branch
+
+### When to Use Cherry-Pick
+
+Cherry-pick is useful when you:
+- Need a bug fix from a feature branch but can't merge the whole branch yet
+- Want to apply a specific commit to a release branch
+- Need to backport a fix to an older version
+- Made a commit on the wrong branch and need to move it
+- Want to duplicate a commit across multiple branches
+
+### Cherry-Pick Creates New Commits
+
+Important: Cherry-picked commits are new commits with different hashes. The original commit remains on the source branch, and a copy is created on the target branch with the same changes but a different commit ID.
+
+## Useful Commands
+
+```bash
+# View commits on another branch
+git log <branch-name> --oneline
+
+# View a specific commit's details
+git show <commit-hash>
+
+# Cherry-pick a single commit
+git cherry-pick <commit-hash>
+
+# Cherry-pick multiple commits
+git cherry-pick <commit-hash1> <commit-hash2>
+
+# Cherry-pick a range of commits
+git cherry-pick <start-hash>..<end-hash>
+
+# If conflicts occur during cherry-pick:
+# 1. Resolve conflicts in files
+# 2. Stage the resolved files
+git add <file>
+# 3. Continue the cherry-pick
+git cherry-pick --continue
+
+# Abort a cherry-pick if something goes wrong
+git cherry-pick --abort
+
+# View commit history graph
+git log --oneline --graph --all
+```
+
+## Verification
+
+Run the verification script to check your solution:
+
+```bash
+.\verify.ps1
+```
+
+The verification will check that:
+- You're on the main branch
+- The security bug fix commit has been applied to main
+- The performance bug fix commit has been applied to main
+- The experimental features are NOT on main
+- The commits were cherry-picked (not merged)
+
+## Challenge Steps
+
+1. Navigate to the challenge directory
+2. You're currently on the development branch
+3. View the commits: `git log --oneline`
+4. You'll see several commits - identify the bug fixes
+5. Switch to main branch: `git checkout main`
+6. Cherry-pick the bug fix commits (you'll need their commit hashes)
+7. Verify the result with `git log --oneline`
+8. Run the verification script
+
+## Tips
+
+- Use `git log development --oneline` to see commits on the development branch
+- Use `git show <hash>` to view details of a specific commit
+- You can cherry-pick by commit hash - you only need the first 7 characters
+- Cherry-pick commits in chronological order (oldest first) to avoid conflicts
+- If you make a mistake, use `.\reset.ps1` to start over
+- The commit message will be preserved when cherry-picking
+
+## Common Cherry-Pick Scenarios
+
+### Hotfix to Production
+You have a critical bug fix on a development branch that needs to go to production immediately:
+```bash
+git checkout production
+git cherry-pick <bugfix-commit-hash>
+```
+
+### Wrong Branch
+You accidentally committed on the wrong branch:
+```bash
+# On wrong branch, note the commit hash
+git log --oneline
+# Switch to correct branch
+git checkout correct-branch
+git cherry-pick <commit-hash>
+# Go back and remove from wrong branch
+git checkout wrong-branch
+git reset --hard HEAD~1
+```
+
+### Backporting
+You need to apply a fix to an older release branch:
+```bash
+git checkout release-2.0
+git cherry-pick <fix-from-main>
+```
+
+## What You'll Learn
+
+Cherry-pick is a surgical tool in your Git toolbox. While merge and rebase work with entire branches, cherry-pick lets you be selective about which changes to apply. This is invaluable for managing hotfixes, maintaining multiple release branches, and handling situations where you need specific changes without bringing along everything else. Understanding when to use cherry-pick versus other Git operations is a mark of Git expertise.
--- a/module-09-cherry-pick/reset.ps1
+++ b/module-09-cherry-pick/reset.ps1
@@ -0,0 +1,22 @@
+#!/usr/bin/env pwsh
+
+<#
+.SYNOPSIS
+    Resets the cherry-pick challenge environment.
+
+.DESCRIPTION
+    Removes the existing challenge directory and runs setup.ps1
+    to create a fresh challenge environment.
+#>
+
+Write-Host "Resetting challenge environment..." -ForegroundColor Yellow
+
+# Remove existing challenge directory if present
+if (Test-Path "challenge") {
+    Remove-Item -Path "challenge" -Recurse -Force
+    Write-Host "Removed existing challenge directory." -ForegroundColor Cyan
+}
+
+# Run setup script
+Write-Host "Running setup script...`n" -ForegroundColor Cyan
+& ".\setup.ps1"
--- a/module-09-cherry-pick/setup.ps1
+++ b/module-09-cherry-pick/setup.ps1
@@ -0,0 +1,208 @@
+#!/usr/bin/env pwsh
+
+<#
+.SYNOPSIS
+    Sets up the cherry-pick challenge environment.
+
+.DESCRIPTION
+    Creates a Git repository with a development branch containing both
+    bug fixes and experimental features. Students must cherry-pick only
+    the bug fixes to the main branch.
+#>
+
+# Remove existing challenge directory if present
+if (Test-Path "challenge") {
+    Write-Host "Removing existing challenge directory..." -ForegroundColor Yellow
+    Remove-Item -Path "challenge" -Recurse -Force
+}
+
+# Create challenge directory
+Write-Host "Creating challenge environment..." -ForegroundColor Cyan
+New-Item -ItemType Directory -Path "challenge" | Out-Null
+Set-Location "challenge"
+
+# Initialize git repository
+git init | Out-Null
+git config user.name "Workshop User" | Out-Null
+git config user.email "user@workshop.local" | Out-Null
+
+# Create initial commits on main branch
+$app = @"
+class App {
+  constructor() {
+    this.version = '1.0.0';
+  }
+
+  start() {
+    console.log('App started');
+  }
+}
+
+module.exports = App;
+"@
+
+Set-Content -Path "app.js" -Value $app
+git add app.js
+git commit -m "Initial app implementation" | Out-Null
+
+$readme = @"
+# Application
+
+Version 1.0.0
+"@
+
+Set-Content -Path "README.md" -Value $readme
+git add README.md
+git commit -m "Add README" | Out-Null
+
+# Create development branch
+git checkout -b development | Out-Null
+
+# Commit 1: Experimental feature (should NOT be cherry-picked)
+$appWithExperimental = @"
+class App {
+  constructor() {
+    this.version = '1.0.0';
+    this.experimentalMode = false;
+  }
+
+  start() {
+    console.log('App started');
+    if (this.experimentalMode) {
+      this.enableExperimentalFeatures();
+    }
+  }
+
+  enableExperimentalFeatures() {
+    console.log('Experimental features enabled');
+  }
+}
+
+module.exports = App;
+"@
+
+Set-Content -Path "app.js" -Value $appWithExperimental
+git add app.js
+git commit -m "Add experimental AI features" | Out-Null
+
+# Commit 2: Security bug fix (SHOULD be cherry-picked)
+$security = @"
+class Security {
+  static sanitizeInput(input) {
+    // Remove potential XSS attacks
+    return input.replace(/[<>]/g, '');
+  }
+
+  static validateToken(token) {
+    if (!token || token.length < 32) {
+      throw new Error('Invalid security token');
+    }
+    return true;
+  }
+}
+
+module.exports = Security;
+"@
+
+Set-Content -Path "security.js" -Value $security
+git add security.js
+git commit -m "Fix security vulnerability in input validation" | Out-Null
+
+# Commit 3: Another experimental feature (should NOT be cherry-picked)
+$appWithMoreExperimental = @"
+class App {
+  constructor() {
+    this.version = '1.0.0';
+    this.experimentalMode = false;
+    this.betaFeatures = [];
+  }
+
+  start() {
+    console.log('App started');
+    if (this.experimentalMode) {
+      this.enableExperimentalFeatures();
+    }
+  }
+
+  enableExperimentalFeatures() {
+    console.log('Experimental features enabled');
+  }
+
+  addBetaFeature(feature) {
+    this.betaFeatures.push(feature);
+  }
+}
+
+module.exports = App;
+"@
+
+Set-Content -Path "app.js" -Value $appWithMoreExperimental
+git add app.js
+git commit -m "Add beta features framework" | Out-Null
+
+# Commit 4: Performance bug fix (SHOULD be cherry-picked)
+$appWithPerformance = @"
+class App {
+  constructor() {
+    this.version = '1.0.0';
+    this.experimentalMode = false;
+    this.betaFeatures = [];
+    this.cache = new Map();
+  }
+
+  start() {
+    console.log('App started');
+    if (this.experimentalMode) {
+      this.enableExperimentalFeatures();
+    }
+  }
+
+  enableExperimentalFeatures() {
+    console.log('Experimental features enabled');
+  }
+
+  addBetaFeature(feature) {
+    this.betaFeatures.push(feature);
+  }
+
+  getData(key) {
+    // Use cache to improve performance
+    if (this.cache.has(key)) {
+      return this.cache.get(key);
+    }
+    const data = this.fetchData(key);
+    this.cache.set(key, data);
+    return data;
+  }
+
+  fetchData(key) {
+    // Simulate data fetching
+    return { key: key, value: 'data' };
+  }
+}
+
+module.exports = App;
+"@
+
+Set-Content -Path "app.js" -Value $appWithPerformance
+git add app.js
+git commit -m "Fix performance issue with data caching" | Out-Null
+
+# Return to module directory
+Set-Location ..
+
+Write-Host "`n========================================" -ForegroundColor Green
+Write-Host "Challenge environment created!" -ForegroundColor Green
+Write-Host "========================================" -ForegroundColor Green
+Write-Host "`nYou are on the 'development' branch with multiple commits:" -ForegroundColor Cyan
+Write-Host "- Experimental features (not ready for production)" -ForegroundColor Yellow
+Write-Host "- Critical bug fixes (needed in production NOW)" -ForegroundColor Green
+Write-Host "`nYour task:" -ForegroundColor Yellow
+Write-Host "1. Navigate to the challenge directory: cd challenge" -ForegroundColor White
+Write-Host "2. View the development branch commits: git log --oneline" -ForegroundColor White
+Write-Host "3. Identify which commits are bug fixes (look for 'Fix' in messages)" -ForegroundColor White
+Write-Host "4. Switch to main branch: git checkout main" -ForegroundColor White
+Write-Host "5. Cherry-pick ONLY the bug fix commits to main" -ForegroundColor White
+Write-Host "6. Do NOT bring the experimental features to main" -ForegroundColor White
+Write-Host "`nHint: Look for commits mentioning 'security' and 'performance' fixes" -ForegroundColor Cyan
+Write-Host "Run '../verify.ps1' from the challenge directory to check your solution.`n" -ForegroundColor Cyan
--- a/module-09-cherry-pick/verify.ps1
+++ b/module-09-cherry-pick/verify.ps1
@@ -0,0 +1,206 @@
+#!/usr/bin/env pwsh
+
+<#
+.SYNOPSIS
+    Verifies the cherry-pick challenge solution.
+
+.DESCRIPTION
+    Checks that the user successfully cherry-picked only the bug fix commits
+    to the main branch without merging the experimental features.
+#>
+
+Set-Location "challenge" -ErrorAction SilentlyContinue
+
+# Check if challenge directory exists
+if (-not (Test-Path "../verify.ps1")) {
+    Write-Host "Error: Please run this script from the module directory" -ForegroundColor Red
+    exit 1
+}
+
+if (-not (Test-Path ".")) {
+    Write-Host "Error: Challenge directory not found. Run setup.ps1 first." -ForegroundColor Red
+    Set-Location ..
+    exit 1
+}
+
+Write-Host "Verifying your solution..." -ForegroundColor Cyan
+
+# Check if git repository exists
+if (-not (Test-Path ".git")) {
+    Write-Host "[FAIL] No git repository found." -ForegroundColor Red
+    Set-Location ..
+    exit 1
+}
+
+# Check current branch
+$currentBranch = git branch --show-current 2>$null
+if ($currentBranch -ne "main") {
+    Write-Host "[FAIL] You should be on the 'main' branch." -ForegroundColor Red
+    Write-Host "Current branch: $currentBranch" -ForegroundColor Yellow
+    Write-Host "Hint: Use 'git checkout main' to switch to main branch" -ForegroundColor Yellow
+    Set-Location ..
+    exit 1
+}
+
+# Check if there's an ongoing cherry-pick
+if (Test-Path ".git/CHERRY_PICK_HEAD") {
+    Write-Host "[FAIL] Cherry-pick is not complete. There may be unresolved conflicts." -ForegroundColor Red
+    Write-Host "Hint: Resolve any conflicts, then use:" -ForegroundColor Yellow
+    Write-Host "  git add <file>" -ForegroundColor White
+    Write-Host "  git cherry-pick --continue" -ForegroundColor White
+    Write-Host "Or abort with: git cherry-pick --abort" -ForegroundColor White
+    Set-Location ..
+    exit 1
+}
+
+# Check commit count on main (should be 4: 2 initial + 2 cherry-picked)
+$mainCommitCount = (git rev-list --count main 2>$null)
+if ($mainCommitCount -ne 4) {
+    Write-Host "[FAIL] Expected 4 commits on main branch, found $mainCommitCount" -ForegroundColor Red
+    if ($mainCommitCount -lt 4) {
+        Write-Host "Hint: You should cherry-pick 2 bug fix commits to main" -ForegroundColor Yellow
+    } else {
+        Write-Host "Hint: You should cherry-pick ONLY the 2 bug fix commits, not all commits" -ForegroundColor Yellow
+    }
+    Write-Host "`nExpected commits on main:" -ForegroundColor Yellow
+    Write-Host "  1. Initial app implementation" -ForegroundColor White
+    Write-Host "  2. Add README" -ForegroundColor White
+    Write-Host "  3. Fix security vulnerability in input validation (cherry-picked)" -ForegroundColor White
+    Write-Host "  4. Fix performance issue with data caching (cherry-picked)" -ForegroundColor White
+    Set-Location ..
+    exit 1
+}
+
+# Check for merge commits (should be none - cherry-pick doesn't create merge commits)
+$mergeCommits = git log --merges --oneline main 2>$null
+if ($mergeCommits) {
+    Write-Host "[FAIL] Found merge commits on main. You should use cherry-pick, not merge." -ForegroundColor Red
+    Write-Host "Hint: Use 'git cherry-pick <commit-hash>' instead of 'git merge'" -ForegroundColor Yellow
+    Set-Location ..
+    exit 1
+}
+
+# Check that security.js exists (from the security fix commit)
+if (-not (Test-Path "security.js")) {
+    Write-Host "[FAIL] security.js not found on main branch." -ForegroundColor Red
+    Write-Host "Hint: You need to cherry-pick the 'Fix security vulnerability' commit" -ForegroundColor Yellow
+    Set-Location ..
+    exit 1
+}
+
+# Check that security.js has the security fix
+$securityContent = Get-Content "security.js" -Raw
+
+if ($securityContent -notmatch "sanitizeInput") {
+    Write-Host "[FAIL] security.js is missing the sanitizeInput function." -ForegroundColor Red
+    Set-Location ..
+    exit 1
+}
+
+if ($securityContent -notmatch "validateToken") {
+    Write-Host "[FAIL] security.js is missing the validateToken function." -ForegroundColor Red
+    Set-Location ..
+    exit 1
+}
+
+# Check that app.js exists
+if (-not (Test-Path "app.js")) {
+    Write-Host "[FAIL] app.js not found." -ForegroundColor Red
+    Set-Location ..
+    exit 1
+}
+
+# Check that app.js has the performance fix (cache) but NOT experimental features
+$appContent = Get-Content "app.js" -Raw
+
+# Should have cache (from performance fix)
+if ($appContent -notmatch "cache") {
+    Write-Host "[FAIL] app.js is missing the performance fix (cache)." -ForegroundColor Red
+    Write-Host "Hint: You need to cherry-pick the 'Fix performance issue' commit" -ForegroundColor Yellow
+    Set-Location ..
+    exit 1
+}
+
+if ($appContent -notmatch "getData") {
+    Write-Host "[FAIL] app.js is missing the getData method from performance fix." -ForegroundColor Red
+    Set-Location ..
+    exit 1
+}
+
+# Should NOT have experimental features
+if ($appContent -match "experimentalMode") {
+    Write-Host "[FAIL] app.js contains experimental features (experimentalMode)." -ForegroundColor Red
+    Write-Host "Hint: You should cherry-pick ONLY the bug fixes, not experimental features" -ForegroundColor Yellow
+    Write-Host "      The experimental feature commits should stay on development branch only" -ForegroundColor Yellow
+    Set-Location ..
+    exit 1
+}
+
+if ($appContent -match "betaFeatures") {
+    Write-Host "[FAIL] app.js contains experimental features (betaFeatures)." -ForegroundColor Red
+    Write-Host "Hint: You should cherry-pick ONLY the bug fixes, not experimental features" -ForegroundColor Yellow
+    Set-Location ..
+    exit 1
+}
+
+if ($appContent -match "enableExperimentalFeatures") {
+    Write-Host "[FAIL] app.js contains experimental features (enableExperimentalFeatures)." -ForegroundColor Red
+    Write-Host "Hint: You should cherry-pick ONLY the bug fixes, not experimental features" -ForegroundColor Yellow
+    Set-Location ..
+    exit 1
+}
+
+# Check commit messages to verify cherry-picks
+$commits = git log --pretty=format:"%s" main 2>$null
+$commitArray = $commits -split "`n"
+
+$hasSecurityFix = $false
+$hasPerformanceFix = $false
+
+foreach ($commit in $commitArray) {
+    if ($commit -match "security vulnerability") {
+        $hasSecurityFix = $true
+    }
+    if ($commit -match "performance issue") {
+        $hasPerformanceFix = $true
+    }
+}
+
+if (-not $hasSecurityFix) {
+    Write-Host "[FAIL] Security fix commit not found on main branch." -ForegroundColor Red
+    Write-Host "Hint: Cherry-pick the 'Fix security vulnerability' commit from development" -ForegroundColor Yellow
+    Set-Location ..
+    exit 1
+}
+
+if (-not $hasPerformanceFix) {
+    Write-Host "[FAIL] Performance fix commit not found on main branch." -ForegroundColor Red
+    Write-Host "Hint: Cherry-pick the 'Fix performance issue' commit from development" -ForegroundColor Yellow
+    Set-Location ..
+    exit 1
+}
+
+# Verify development branch still has all commits
+$devCommitCount = (git rev-list --count development 2>$null)
+if ($devCommitCount -ne 6) {
+    Write-Host "[FAIL] Development branch should still have 6 commits." -ForegroundColor Red
+    Write-Host "Found: $devCommitCount commits" -ForegroundColor Yellow
+    Set-Location ..
+    exit 1
+}
+
+# Success!
+Write-Host "`n========================================" -ForegroundColor Green
+Write-Host "SUCCESS! Challenge completed!" -ForegroundColor Green
+Write-Host "========================================" -ForegroundColor Green
+Write-Host "`nYou have successfully:" -ForegroundColor Cyan
+Write-Host "- Cherry-picked the security vulnerability fix to main" -ForegroundColor White
+Write-Host "- Cherry-picked the performance issue fix to main" -ForegroundColor White
+Write-Host "- Left experimental features on development branch only" -ForegroundColor White
+Write-Host "- Kept development branch intact with all commits" -ForegroundColor White
+Write-Host "`nPerfect use of cherry-pick!" -ForegroundColor Green
+Write-Host "You selectively applied critical fixes without merging unfinished features.`n" -ForegroundColor Green
+Write-Host "Try 'git log --oneline --graph --all' to see both branches." -ForegroundColor Cyan
+
+Set-Location ..
+exit 0