98 lines
3.3 KiB
Markdown
98 lines
3.3 KiB
Markdown
# Module 04: Merging
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## Learning Objectives
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In this module, you will:
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- Understand what merging means in Git
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- Perform a fast-forward merge
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- Perform a three-way merge
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- Understand when merge commits are created
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- Use `git merge` to combine branches
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## Challenge
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### Setup
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Run the setup script to create your challenge environment:
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```powershell
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.\setup.ps1
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```
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This will create a `challenge/` directory with a Git repository that has a main branch and a feature branch ready to merge.
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### Your Task
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This challenge has two parts that teach you about the two types of merges in Git:
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**Part 1: Fast-Forward Merge**
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1. Merge the existing `feature-api` branch into main
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2. Observe that this is a "fast-forward" merge (no merge commit created)
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**Part 2: Three-Way Merge**
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3. Create a new branch called `feature-ui`
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4. Make commits on the feature-ui branch
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5. Switch back to main and make a commit there too (creates divergence)
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6. Merge feature-ui into main
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7. Observe that this creates a merge commit (three-way merge)
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**Suggested Approach:**
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1. Navigate to the challenge directory: `cd challenge`
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2. Check current branch: `git branch` (should be on main)
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3. View existing branches: `git branch -a`
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4. Merge feature-api: `git merge feature-api`
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5. View the log: `git log --oneline --graph`
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6. Create feature-ui branch: `git checkout -b feature-ui`
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7. Create a new file `ui.py` and commit it
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8. Make another commit on feature-ui (modify ui.py)
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9. Switch back to main: `git checkout main`
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10. Make a change on main (modify api.py) and commit it
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11. Merge feature-ui: `git merge feature-ui`
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12. View the merge history: `git log --oneline --graph --all`
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> **Important Notes:**
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> - A **fast-forward merge** happens when main hasn't changed since the feature branch was created
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> - A **three-way merge** creates a merge commit when both branches have diverged
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> - You can see merge commits with `git log --merges`
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> - The `--graph` option helps visualize the branch history
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> - After merging, the feature branch still exists but you can delete it with `git branch -d`
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## Key Concepts
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- **Merge**: Combining changes from different branches into one branch.
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- **Fast-Forward Merge**: When the target branch hasn't changed, Git simply moves the branch pointer forward. No merge commit is created.
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- **Three-Way Merge**: When both branches have new commits, Git creates a merge commit that has two parent commits.
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- **Merge Commit**: A special commit with two (or more) parent commits, representing the point where branches were merged.
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- **Divergent Branches**: Branches that have different commits since they split from a common ancestor.
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## Useful Commands
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```bash
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git merge <branch> # Merge branch into current branch
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git log --oneline --graph # View merge history visually
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git log --graph --all # View all branches and merges
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git log --merges # Show only merge commits
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git branch -d <branch> # Delete a merged branch (optional)
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```
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## Verification
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Once you've completed both merges, verify your solution:
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```powershell
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.\verify.ps1
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```
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The verification script will check that you've successfully merged both feature branches and understand the different merge types.
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## Need to Start Over?
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If you want to reset the challenge and start fresh:
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```powershell
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.\reset.ps1
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```
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This will remove the challenge directory and run the setup script again, giving you a clean slate.
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