git-workshop/module-05-conflicts

Module 05: Merge Conflicts

Learning Objectives

In this module, you will:

• Understand what merge conflicts are and why they occur
• Recognize conflict markers in files
• Manually resolve merge conflicts
• Complete a merge after resolving conflicts
• Use git status to identify conflicted files

Challenge

Setup

Run the setup script to create your challenge environment:

.\setup.ps1

This will create a challenge/ directory with a Git repository that has conflicting changes on two branches.

Your Task

You will intentionally create and resolve a merge conflict - a crucial skill for collaborative development!

The Scenario:

• The main branch and feature-updates branch both modified the same lines in app.py
• When you try to merge them, Git can't automatically resolve the differences
• You must manually resolve the conflict

Steps:

1. Navigate to the challenge directory: cd challenge
2. Verify you're on main: git branch
3. Attempt to merge feature-updates: git merge feature-updates
4. Git will report a conflict! Don't panic - this is expected
5. Check status: git status (shows conflicted files)
6. Open app.py in a text editor
7. Look for conflict markers:

   <<<<<<< HEAD
   (your current branch's version)
   =======
   (the other branch's version)
   >>>>>>> feature-updates
   

8. Manually resolve by editing the file:
   • Remove the conflict markers (<<<<<<<, =======, >>>>>>>)
   • Keep the version you want, or combine both changes
9. Save the file
10. Mark as resolved: git add app.py
11. Complete the merge: git commit
12. View the result: git log --oneline --graph

Important Notes:

• Conflicts occur when the same lines are changed differently in both branches
• Conflict markers show both versions - you choose what to keep
• You can keep one version, the other, or combine them creatively
• After editing, you MUST git add to mark the conflict as resolved
• Then git commit to complete the merge
• Use git merge --abort if you want to cancel and start over

Key Concepts

• Merge Conflict: Occurs when the same lines in a file are changed differently in both branches being merged.
• Conflict Markers: Special markers Git inserts to show the conflicting versions:
  • <<<<<<< HEAD: Marks the start of your current branch's changes
  • =======: Separates the two conflicting versions
  • >>>>>>> branch-name: Marks the end of the other branch's changes
• Conflict Resolution: The process of manually editing the file to resolve the differences and remove conflict markers.
• Staging Resolution: Using git add to tell Git you've resolved the conflict.

Useful Commands

git merge <branch>           # Attempt merge (may cause conflict)
git status                   # See which files have conflicts
git diff                     # View conflicts in detail
cat <file>                   # View file with conflict markers
git add <file>               # Mark conflict as resolved
git commit                   # Complete the merge
git commit -m "message"      # Complete merge with message
git merge --abort            # Cancel merge and go back

Verification

Once you've resolved the conflict and completed the merge, verify your solution:

.\verify.ps1

The verification script will check that you've successfully resolved the conflict and completed the merge.

Need to Start Over?

If you want to reset the challenge and start fresh:

.\reset.ps1

This will remove the challenge directory and run the setup script again, giving you a clean slate.