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refactor: rewrite the merge-revert section

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It is an advanced and difficult revert to accomplish and should probably
be done through a reset instead, which means that we're modifying
history which is dangerous and so should be handled by someone who
understands these dangers.
This commit is contained in:
Bjarke Sporring
2026-01-15 16:11:24 +01:00
parent aa24c50b45
commit 575e083f33
4 changed files with 186 additions and 282 deletions
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268
01-essentials/06-revert/README.md
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@@ -1,8 +1,8 @@
# Module 05: Git Revert - Safe Undoing # Module 06: Git Revert - Safe Undoing
## About This Module ## About This Module
Welcome to Module 05, where you'll learn the **safe, team-friendly way to undo changes** in Git. Unlike destructive commands that erase history, `git revert` creates new commits that undo previous changes while preserving the complete project history. Welcome to Module 06, where you'll learn the **safe, team-friendly way to undo changes** in Git. Unlike destructive commands that erase history, `git revert` creates new commits that undo previous changes while preserving the complete project history.
**Why revert is important:** **Why revert is important:**
- ✅ Safe for shared/pushed commits - ✅ Safe for shared/pushed commits
@@ -17,19 +17,18 @@ Welcome to Module 05, where you'll learn the **safe, team-friendly way to undo c
By completing this module, you will: By completing this module, you will:
1. Revert regular commits safely while preserving surrounding changes 1. Revert commits safely while preserving surrounding changes
2. Revert merge commits using the `-m` flag 2. Revert old commits in the middle of history
3. Understand merge commit parent numbering 3. Understand how revert preserves commits before and after the target
4. Handle the re-merge problem that occurs after reverting merges 4. Revert multiple commits at once
5. Revert multiple commits at once 5. Know when to use revert vs. other undo strategies
6. Know when to use revert vs. other undo strategies
## Prerequisites ## Prerequisites
Before starting this module, you should be comfortable with: Before starting this module, you should be comfortable with:
- Creating commits (`git commit`) - Creating commits (`git commit`)
- Viewing commit history (`git log`) - Viewing commit history (`git log`)
- Understanding branches and merging (Module 03) - Understanding branches (Module 03)
## Setup ## Setup
@@ -41,7 +40,7 @@ Run the setup script to create the challenge environment:
This creates a `challenge/` directory with three branches demonstrating different revert scenarios: This creates a `challenge/` directory with three branches demonstrating different revert scenarios:
- `regular-revert` - Basic commit reversion - `regular-revert` - Basic commit reversion
- `merge-revert` - Merge commit reversion - `middle-revert` - Reverting a commit in the middle of history
- `multi-revert` - Multiple commit reversion - `multi-revert` - Multiple commit reversion
## Challenge 1: Reverting a Regular Commit ## Challenge 1: Reverting a Regular Commit
@@ -120,140 +119,108 @@ main.py (initial) → multiply (good) → divide (BAD) → modulo (good) → rev
The revert commit adds a new point in history that undoes the divide changes. The revert commit adds a new point in history that undoes the divide changes.
## Challenge 2: Reverting a Merge Commit ## Challenge 2: Reverting a Commit in the Middle
### Scenario ### Scenario
Your team merged a `feature-auth` branch that added authentication functionality. After deployment, you discovered the authentication system has critical security issues. You need to revert the entire merge while the security team redesigns the feature. You're working on improving your calculator application. Several commits were made in sequence:
1. Added input validation (good)
2. Added output formatter (BAD - has bugs!)
3. Added configuration module (good - but came after the bad commit)
**This is different from reverting a regular commit!** Merge commits have **two parents**, so you must tell Git which parent to keep. The formatter has critical bugs and needs to be removed, but you want to keep both the validation module (added before) and the configuration module (added after).
### Understanding Merge Commit Parents **This demonstrates an important Git principle:** Revert works on ANY commit in history, not just recent ones!
When you merge a feature branch into main: ### Understanding History Preservation
Here's what the commit history looks like:
``` ```
feature-auth (parent 2) A (initial) → B (validation) → C (formatter BAD) → D (config)
↓
C---D
/ \
A---B-----M ← Merge commit (has TWO parents)
↑ ↑
parent 1 (main) We want to remove THIS
``` ```
The merge commit `M` has: When you revert commit C:
- **Parent 1**: The branch you merged INTO (main)
- **Parent 2**: The branch you merged FROM (feature-auth)
When reverting a merge, you must specify which parent to keep using the `-m` flag: ```
- `-m 1` means "keep parent 1" (main) - **Most common** A (initial) → B (validation) → C (formatter BAD) → D (config) → E (revert C)
- `-m 2` means "keep parent 2" (feature-auth) - Rare ↑
Removes formatter, keeps validation & config
```
**In practice:** You almost always use `-m 1` to keep the main branch and undo the feature branch changes. **Key insight:** The revert creates a NEW commit (E) that undoes commit C, but leaves B and D completely intact!
### Your Task ### Your Task
1. **Switch to the merge-revert branch:** 1. **Switch to the middle-revert branch:**
```pwsh ```pwsh
git switch merge-revert git switch middle-revert
``` ```
2. **View the commit history with the graph:** 2. **View the commit history:**
```pwsh ```pwsh
git log --oneline --graph git log --oneline
``` ```
Look for the merge commit message: "Merge feature-auth branch" You should see three commits after the initial:
- Note the commit hash - "Add input validation module"
- Write it down or copy it - "Add broken formatter - needs to be reverted!"
- "Add configuration module"
3. **Revert the merge commit using `-m 1`** (replace `<merge-commit-hash>` with actual hash): 3. **Find the broken formatter commit:**
- Look for the message: "Add broken formatter - needs to be reverted!"
- Note the commit hash (the 7-character code)
- Write it down
4. **Revert that middle commit** (replace `<commit-hash>` with actual hash):
```pwsh ```pwsh
git revert -m 1 <merge-commit-hash> git revert <commit-hash>
``` ```
**What `-m 1` means:** 5. **Visual Studio Code will open** with the revert commit message:
- `-m 1` tells Git to keep parent 1 (the main branch side) - The default message is fine
- This undoes all changes from the feature-auth branch
- Creates a new "revert merge" commit
4. **Visual Studio Code will open** with the revert commit message:
- Close the editor window to accept it - Close the editor window to accept it
- Git will create the revert commit - Git will create the revert commit
5. **Check the result:** 6. **Check the result:**
```pwsh ```pwsh
# View files - auth.py should be gone # View files - formatter.py should be gone
ls ls
# You should see calculator.py but NOT auth.py # You should see validation.py and config.py but NOT formatter.py
# Verify calculator.py no longer imports auth # View the history
cat calculator.py git log --oneline
# Should NOT see "from auth import" anywhere # You should see the new revert commit at the top
``` ```
### What Happens Without -m? ### What to Observe
If you try to revert a merge commit without the `-m` flag: After reverting, notice:
```bash ```pwsh
git revert <merge-commit-hash> # Check which files exist
# Error: commit <hash> is a merge but no -m option was given ls
# You should see:
# - calculator.py (from initial commit)
# - validation.py (from commit BEFORE bad one) ✅
# - config.py (from commit AFTER bad one) ✅
# - formatter.py is GONE (reverted) ❌
``` ```
Git doesn't know which parent you want to keep, so it refuses to proceed. **Important:** Git successfully removed the bad formatter while keeping everything else!
### The Re-Merge Problem ### Why This Matters
**Important gotcha:** After reverting a merge, you **cannot simply re-merge** the same branch! This scenario demonstrates revert's power in real-world situations:
- You discover a bug in code committed days or weeks ago
- Many commits have been made since then
- You can't just delete the old commit (that would break history)
- Revert lets you surgically remove just the bad commit
Here's why: **Revert is your "undo button" for shared history!**
```
Initial merge:
A---B---M (merged feature-auth)
↑
All changes from feature-auth are now in main
After revert:
A---B---M---R (reverted merge)
↑
Changes removed, but Git remembers they were merged
Attempting to re-merge:
A---B---M---R---M2 (try to merge feature-auth again)
↑
Git thinks: "I already merged these commits,
nothing new to add!" (Empty merge)
```
**Solutions if you need to re-merge:**
1. **Revert the revert** (recommended):
```bash
git revert <revert-commit-hash>
```
This brings back all the feature-auth changes.
2. **Cherry-pick new commits** from the feature branch:
```bash
git cherry-pick <new-commits>
```
3. **Merge with --no-ff** and resolve conflicts manually (advanced).
### When to Revert Merges
Revert merge commits when:
- ✅ Feature causes production issues
- ✅ Need to temporarily remove a feature
- ✅ Discovered critical bugs after merging
- ✅ Security issues require immediate rollback
Don't revert merges when:
- ❌ You just need to fix a small bug (fix it with a new commit instead)
- ❌ You plan to re-merge the same branch soon (use reset if local, or revert-the-revert later)
## Challenge 3: Reverting Multiple Commits ## Challenge 3: Reverting Multiple Commits
@@ -311,7 +278,7 @@ Two separate commits added broken mathematical functions (`square_root` and `log
**Reverting a range of commits:** **Reverting a range of commits:**
```bash ```pwsh
# Revert commits from A to B (inclusive) # Revert commits from A to B (inclusive)
git revert A^..B git revert A^..B
@@ -321,7 +288,7 @@ git revert HEAD~3..HEAD
**Reverting without auto-commit:** **Reverting without auto-commit:**
```bash ```pwsh
# Stage revert changes without committing # Stage revert changes without committing
git revert --no-commit <commit-hash> git revert --no-commit <commit-hash>
@@ -353,8 +320,7 @@ The script checks that:
- ✅ Revert commits were created (not destructive deletion) - ✅ Revert commits were created (not destructive deletion)
- ✅ Bad code is removed - ✅ Bad code is removed
- ✅ Good code before and after is preserved - ✅ Good code before and after is preserved
- ✅ Merge commits still exist in history - ✅ Revert works on commits in the middle of history
- ✅ Proper use of `-m` flag for merge reverts
## Command Reference ## Command Reference
@@ -371,14 +337,17 @@ git revert HEAD
git revert HEAD~1 git revert HEAD~1
``` ```
### Merge Commit Revert ### Reverting Old Commits
```pwsh ```pwsh
# Revert a merge commit (keep parent 1) # Revert a specific commit from any point in history
git revert -m 1 <merge-commit-hash> git revert <commit-hash>
# Revert a merge commit (keep parent 2) - rare # Revert a commit from 5 commits ago
git revert -m 2 <merge-commit-hash> git revert HEAD~5
# View what a commit changed before reverting
git show <commit-hash>
``` ```
### Multiple Commits ### Multiple Commits
@@ -450,7 +419,7 @@ Consider alternatives when:
Sometimes reverting causes conflicts if subsequent changes touched the same code: Sometimes reverting causes conflicts if subsequent changes touched the same code:
```bash ```pwsh
# Start revert # Start revert
git revert <commit-hash> git revert <commit-hash>
@@ -463,47 +432,24 @@ git revert <commit-hash>
1. Open conflicted files and fix conflicts (look for `<<<<<<<` markers) 1. Open conflicted files and fix conflicts (look for `<<<<<<<` markers)
2. Stage resolved files: 2. Stage resolved files:
```bash ```pwsh
git add <resolved-files> git add <resolved-files>
``` ```
3. Continue the revert: 3. Continue the revert:
```bash ```pwsh
git revert --continue git revert --continue
``` ```
Or abort if you change your mind: Or abort if you change your mind:
```bash ```pwsh
git revert --abort git revert --abort
``` ```
## Common Mistakes ## Common Mistakes
### 1. Forgetting -m for Merge Commits ### 1. Using Reset on Pushed Commits
```bash ```pwsh
# ❌ Wrong - will fail
git revert <merge-commit>
# ✅ Correct
git revert -m 1 <merge-commit>
```
### 2. Trying to Re-Merge After Revert
```bash
# After reverting a merge:
git revert -m 1 <merge-commit>
# ❌ This won't work as expected
git merge feature-branch # Empty merge!
# ✅ Do this instead
git revert <the-revert-commit> # Revert the revert
```
### 3. Using Reset on Pushed Commits
```bash
# ❌ NEVER do this with pushed commits # ❌ NEVER do this with pushed commits
git reset --hard HEAD~3 git reset --hard HEAD~3
@@ -511,11 +457,11 @@ git reset --hard HEAD~3
git revert HEAD~3..HEAD git revert HEAD~3..HEAD
``` ```
### 4. Reverting Commits in Wrong Order ### 2. Reverting Commits in Wrong Order
When reverting multiple related commits, revert from newest to oldest: When reverting multiple related commits, revert from newest to oldest:
```bash ```pwsh
# If you have: A → B → C (and C depends on B) # If you have: A → B → C (and C depends on B)
# ✅ Correct order # ✅ Correct order
@@ -530,7 +476,7 @@ git revert C
## Best Practices ## Best Practices
1. **Write clear revert messages:** 1. **Write clear revert messages:**
```bash ```pwsh
git revert <hash> -m "Revert authentication - security issue #1234" git revert <hash> -m "Revert authentication - security issue #1234"
``` ```
@@ -561,15 +507,6 @@ git revert C
## Troubleshooting ## Troubleshooting
### "Commit is a merge but no -m option was given"
**Problem:** Trying to revert a merge commit without `-m`.
**Solution:**
```bash
git revert -m 1 <merge-commit-hash>
```
### "Empty Revert / No Changes" ### "Empty Revert / No Changes"
**Problem:** Revert doesn't seem to do anything. **Problem:** Revert doesn't seem to do anything.
@@ -580,7 +517,7 @@ git revert -m 1 <merge-commit-hash>
- Wrong commit hash - Wrong commit hash
**Solution:** **Solution:**
```bash ```pwsh
# Check what the commit actually changed # Check what the commit actually changed
git show <commit-hash> git show <commit-hash>
@@ -601,24 +538,22 @@ git log --grep="Revert"
Or consider fixing forward with a new commit instead of reverting. Or consider fixing forward with a new commit instead of reverting.
### "Can't Re-Merge After Reverting Merge" ### "Reverting Old Commit Breaks Something"
**Problem:** After reverting a merge, re-merging the branch brings no changes. **Problem:** After reverting an old commit, something else stops working.
**Solution:** Revert the revert commit: **Why:** The old commit might have been a dependency for later commits.
```bash
# Find the revert commit
git log --oneline
# Revert the revert (brings changes back) **Solution:**
git revert <revert-commit-hash> 1. Check what changed: `git diff HEAD~1 HEAD`
``` 2. Either fix the issue with a new commit, or
3. Revert the revert if needed: `git revert <revert-commit-hash>`
## Advanced: Revert Internals ## Advanced: Revert Internals
Understanding what revert does under the hood: Understanding what revert does under the hood:
```bash ```pwsh
# Revert creates a new commit with inverse changes # Revert creates a new commit with inverse changes
git revert <commit-hash> git revert <commit-hash>
@@ -645,9 +580,8 @@ You've learned:
- ✅ `git revert` creates new commits that undo previous changes - ✅ `git revert` creates new commits that undo previous changes
- ✅ Revert is safe for shared/pushed commits - ✅ Revert is safe for shared/pushed commits
- ✅ Merge commits require `-m 1` or `-m 2` flag - ✅ Revert works on any commit in history, even old ones
- ✅ Parent 1 = branch merged into, Parent 2 = branch merged from - ✅ Commits before and after the reverted commit are preserved
- ✅ Can't simply re-merge after reverting a merge
- ✅ Multiple commits can be reverted in one command - ✅ Multiple commits can be reverted in one command
- ✅ Revert preserves complete history for audit trails - ✅ Revert preserves complete history for audit trails

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01-essentials/06-revert/reset.ps1
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@@ -1,14 +1,14 @@
#!/usr/bin/env pwsh #!/usr/bin/env pwsh
<# <#
.SYNOPSIS .SYNOPSIS
Resets the Module 05 challenge environment to start fresh. Resets the Module 06 challenge environment to start fresh.
.DESCRIPTION .DESCRIPTION
This script removes the challenge directory and re-runs setup.ps1 This script removes the challenge directory and re-runs setup.ps1
to create a fresh challenge environment. to create a fresh challenge environment.
#> #>
Write-Host "`n=== Resetting Module 05: Git Revert Challenge ===" -ForegroundColor Cyan Write-Host "`n=== Resetting Module 06: Git Revert Challenge ===" -ForegroundColor Cyan
# Check if challenge directory exists # Check if challenge directory exists
if (Test-Path "challenge") { if (Test-Path "challenge") {

119
01-essentials/06-revert/setup.ps1
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@@ -1,17 +1,17 @@
#!/usr/bin/env pwsh #!/usr/bin/env pwsh
<# <#
.SYNOPSIS .SYNOPSIS
Sets up the Module 05 challenge environment for learning git revert. Sets up the Module 06 challenge environment for learning git revert.
.DESCRIPTION .DESCRIPTION
This script creates a challenge directory with three branches demonstrating This script creates a challenge directory with three branches demonstrating
different revert scenarios: different revert scenarios:
- regular-revert: Basic revert of a single bad commit - regular-revert: Basic revert of a single bad commit at the end
- merge-revert: Reverting a merge commit with -m flag - middle-revert: Reverting a bad commit in the middle of history
- multi-revert: Reverting multiple commits at once - multi-revert: Reverting multiple commits at once
#> #>
Write-Host "`n=== Setting up Module 05: Git Revert Challenge ===" -ForegroundColor Cyan Write-Host "`n=== Setting up Module 06: Git Revert Challenge ===" -ForegroundColor Cyan
# Remove existing challenge directory if it exists # Remove existing challenge directory if it exists
if (Test-Path "challenge") { if (Test-Path "challenge") {
@@ -104,90 +104,63 @@ git commit -m "Add modulo function" | Out-Null
Write-Host "[CREATED] regular-revert branch with bad divide commit" -ForegroundColor Green Write-Host "[CREATED] regular-revert branch with bad divide commit" -ForegroundColor Green
# ============================================================================ # ============================================================================
# SCENARIO 2: Merge Revert (Merge Commit with -m flag) # SCENARIO 2: Revert in Middle of History
# ============================================================================ # ============================================================================
Write-Host "`nScenario 2: Creating merge-revert scenario..." -ForegroundColor Cyan Write-Host "`nScenario 2: Creating middle-revert scenario..." -ForegroundColor Cyan
# Switch back to main # Switch back to main
git switch $mainBranch | Out-Null git switch $mainBranch | Out-Null
# Create merge-revert branch # Create middle-revert branch
git switch -c merge-revert | Out-Null git switch -c middle-revert | Out-Null
# Create a feature branch to merge # Good commit: Add validation module
git switch -c feature-auth | Out-Null $validationContent = @"
# validation.py - Input validation
# Add auth functionality def validate_number(value):
$authContent = @" """Check if value is a valid number."""
# auth.py - Authentication module try:
float(value)
def login(username, password):
\"\"\"Login user.\"\"\"
print(f"Logging in {username}...")
return True return True
except ValueError:
def logout(username):
\"\"\"Logout user.\"\"\"
print(f"Logging out {username}...")
return True
"@
Set-Content -Path "auth.py" -Value $authContent
git add .
git commit -m "Add authentication module" | Out-Null
# Add password validation
$authContent = @"
# auth.py - Authentication module
def validate_password(password):
\"\"\"Validate password strength.\"\"\"
return len(password) >= 8
def login(username, password):
\"\"\"Login user.\"\"\"
if not validate_password(password):
print("Password too weak!")
return False return False
print(f"Logging in {username}...")
return True
def logout(username):
\"\"\"Logout user.\"\"\"
print(f"Logging out {username}...")
return True
"@ "@
Set-Content -Path "auth.py" -Value $authContent Set-Content -Path "validation.py" -Value $validationContent
git add . git add .
git commit -m "Add password validation" | Out-Null git commit -m "Add input validation module" | Out-Null
# Integrate auth into calculator (part of the feature branch) # BAD commit: Add broken formatter
$calcContent = @" $formatterContent = @"
# calculator.py - Simple calculator # formatter.py - Output formatting
from auth import login
def add(a, b): def format_result(result):
"""Add two numbers.""" """BROKEN: Doesn't handle None or errors properly!"""
return a + b return f"Result: {result.upper()}" # This crashes if result is not a string!
def subtract(a, b):
"""Subtract b from a."""
return a - b
def secure_divide(a, b, username):
"""Secure divide - requires authentication."""
if login(username, "password123"):
return a / b
return None
"@ "@
Set-Content -Path "calculator.py" -Value $calcContent Set-Content -Path "formatter.py" -Value $formatterContent
git add . git add .
git commit -m "Integrate auth into calculator" | Out-Null git commit -m "Add broken formatter - needs to be reverted!" | Out-Null
# Switch back to merge-revert and merge feature-auth # Good commit: Add configuration (depends on validation, not formatter)
git switch merge-revert | Out-Null $configContent = @"
git merge feature-auth --no-ff -m "Merge feature-auth branch" | Out-Null # config.py - Application configuration
Write-Host "[CREATED] merge-revert branch with merge commit to revert" -ForegroundColor Green from validation import validate_number
DEFAULT_PRECISION = 2
def set_precision(value):
"""Set calculation precision."""
if validate_number(value):
return int(value)
return DEFAULT_PRECISION
"@
Set-Content -Path "config.py" -Value $configContent
git add .
git commit -m "Add configuration module" | Out-Null
Write-Host "[CREATED] middle-revert branch with bad commit in the middle" -ForegroundColor Green
# ============================================================================ # ============================================================================
# SCENARIO 3: Multi Revert (Multiple Bad Commits) # SCENARIO 3: Multi Revert (Multiple Bad Commits)
@@ -275,8 +248,8 @@ Set-Location ..
Write-Host "`n=== Setup Complete! ===" -ForegroundColor Green Write-Host "`n=== Setup Complete! ===" -ForegroundColor Green
Write-Host "`nThree revert scenarios have been created:" -ForegroundColor Cyan Write-Host "`nThree revert scenarios have been created:" -ForegroundColor Cyan
Write-Host " 1. regular-revert - Revert a single bad commit (basic)" -ForegroundColor White Write-Host " 1. regular-revert - Revert a bad commit at the end" -ForegroundColor White
Write-Host " 2. merge-revert - Revert a merge commit with -m flag" -ForegroundColor White Write-Host " 2. middle-revert - Revert a bad commit in the middle of history" -ForegroundColor White
Write-Host " 3. multi-revert - Revert multiple bad commits" -ForegroundColor White Write-Host " 3. multi-revert - Revert multiple bad commits" -ForegroundColor White
Write-Host "`nYou are currently on the 'regular-revert' branch." -ForegroundColor Cyan Write-Host "`nYou are currently on the 'regular-revert' branch." -ForegroundColor Cyan
Write-Host "`nNext steps:" -ForegroundColor Cyan Write-Host "`nNext steps:" -ForegroundColor Cyan

79
01-essentials/06-revert/verify.ps1
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@@ -1,16 +1,16 @@
#!/usr/bin/env pwsh #!/usr/bin/env pwsh
<# <#
.SYNOPSIS .SYNOPSIS
Verifies the Module 05 challenge solutions. Verifies the Module 06 challenge solutions.
.DESCRIPTION .DESCRIPTION
Checks that all three revert scenarios have been completed correctly: Checks that all three revert scenarios have been completed correctly:
- regular-revert: Single commit reverted - regular-revert: Single commit reverted
- merge-revert: Merge commit reverted with -m flag - middle-revert: Commit in middle of history reverted
- multi-revert: Multiple commits reverted - multi-revert: Multiple commits reverted
#> #>
Write-Host "`n=== Verifying Module 05: Git Revert Solutions ===" -ForegroundColor Cyan Write-Host "`n=== Verifying Module 06: Git Revert Solutions ===" -ForegroundColor Cyan
$allChecksPassed = $true $allChecksPassed = $true
$originalDir = Get-Location $originalDir = Get-Location
@@ -87,53 +87,50 @@ if ($LASTEXITCODE -ne 0) {
} }
# ============================================================================ # ============================================================================
# SCENARIO 2: Merge Revert Verification # SCENARIO 2: Middle Revert Verification
# ============================================================================ # ============================================================================
Write-Host "`n=== Scenario 2: Merge Revert ===" -ForegroundColor Cyan Write-Host "`n=== Scenario 2: Middle Revert ===" -ForegroundColor Cyan
git switch merge-revert 2>&1 | Out-Null git switch middle-revert 2>&1 | Out-Null
if ($LASTEXITCODE -ne 0) { if ($LASTEXITCODE -ne 0) {
Write-Host "[FAIL] merge-revert branch not found" -ForegroundColor Red Write-Host "[FAIL] middle-revert branch not found" -ForegroundColor Red
$allChecksPassed = $false $allChecksPassed = $false
} else { } else {
# Check that a revert commit for the merge exists # Check that a revert commit exists
$revertMerge = git log --oneline --grep="Revert.*Merge" 2>$null $revertCommit = git log --oneline --grep="Revert" 2>$null
if ($revertMerge) { if ($revertCommit) {
Write-Host "[PASS] Merge revert commit found" -ForegroundColor Green Write-Host "[PASS] Revert commit found" -ForegroundColor Green
} else { } else {
Write-Host "[FAIL] No merge revert commit found" -ForegroundColor Red Write-Host "[FAIL] No revert commit found" -ForegroundColor Red
Write-Host "[HINT] Use: git revert -m 1 <merge-commit-hash>" -ForegroundColor Yellow Write-Host "[HINT] Use: git revert <commit-hash>" -ForegroundColor Yellow
$allChecksPassed = $false $allChecksPassed = $false
} }
# Check that the original merge commit still exists (revert doesn't erase it) # Check that formatter.py is removed (reverted)
$mergeCommit = git log --merges --oneline --grep="Merge feature-auth" 2>$null if (-not (Test-Path "formatter.py")) {
if ($mergeCommit) { Write-Host "[PASS] Broken formatter.py successfully reverted (file removed)" -ForegroundColor Green
Write-Host "[PASS] Original merge commit still in history (not erased)" -ForegroundColor Green
} else { } else {
Write-Host "[INFO] Original merge commit not found (this is OK if you used a different approach)" -ForegroundColor Yellow Write-Host "[FAIL] formatter.py still exists (should be reverted)" -ForegroundColor Red
} Write-Host "[HINT] The bad commit should be reverted, removing formatter.py" -ForegroundColor Yellow
# Check that auth.py no longer exists or its effects are reverted
if (-not (Test-Path "auth.py")) {
Write-Host "[PASS] auth.py removed (merge reverted successfully)" -ForegroundColor Green
} else {
Write-Host "[INFO] auth.py still exists (check if merge was fully reverted)" -ForegroundColor Yellow
}
# Check that calculator.py exists
if (Test-Path "calculator.py") {
$calcContent = Get-Content "calculator.py" -Raw
# After reverting the merge, calculator shouldn't import auth
if ($calcContent -notmatch "from auth import") {
Write-Host "[PASS] Auth integration reverted from calculator.py" -ForegroundColor Green
} else {
Write-Host "[FAIL] calculator.py still imports auth (merge not fully reverted)" -ForegroundColor Red
Write-Host "[HINT] Reverting the merge should remove the auth integration" -ForegroundColor Yellow
$allChecksPassed = $false $allChecksPassed = $false
} }
# Check that validation.py still exists (good commit before bad one)
if (Test-Path "validation.py") {
Write-Host "[PASS] validation.py preserved (good commit before bad one)" -ForegroundColor Green
} else {
Write-Host "[FAIL] validation.py missing (should still exist)" -ForegroundColor Red
$allChecksPassed = $false
}
# Check that config.py still exists (good commit after bad one)
if (Test-Path "config.py") {
Write-Host "[PASS] config.py preserved (good commit after bad one)" -ForegroundColor Green
} else {
Write-Host "[FAIL] config.py missing (should still exist)" -ForegroundColor Red
Write-Host "[HINT] Only revert the bad commit, not the good ones after it" -ForegroundColor Yellow
$allChecksPassed = $false
} }
} }
@@ -211,11 +208,11 @@ if ($allChecksPassed) {
Write-Host "=========================================" -ForegroundColor Green Write-Host "=========================================" -ForegroundColor Green
Write-Host "`nYou've mastered git revert!" -ForegroundColor Cyan Write-Host "`nYou've mastered git revert!" -ForegroundColor Cyan
Write-Host "You now understand:" -ForegroundColor Cyan Write-Host "You now understand:" -ForegroundColor Cyan
Write-Host " ✓ Reverting regular commits safely" -ForegroundColor White Write-Host " ✓ Reverting commits safely without erasing history" -ForegroundColor White
Write-Host " ✓ Reverting merge commits with -m flag" -ForegroundColor White Write-Host " ✓ Reverting old commits in the middle of history" -ForegroundColor White
Write-Host " ✓ Reverting multiple commits at once" -ForegroundColor White Write-Host " ✓ Reverting multiple commits at once" -ForegroundColor White
Write-Host " ✓ Preserving history while undoing changes" -ForegroundColor White Write-Host " ✓ Preserving commits before and after the reverted one" -ForegroundColor White
Write-Host "`nReady for Module 06: Git Reset!" -ForegroundColor Green Write-Host "`nReady for Module 07: Git Reset!" -ForegroundColor Green
Write-Host "" Write-Host ""
exit 0 exit 0
} else { } else {