Feat(multi-store users): Deploy theme changes across multiple stores without manual conflict resolution

[lmcrean]

Unique store settings are preserved via configured Git merge drivers.

Problem

Fixes #3509

When working with themes across multiple stores, developers encounter merge conflicts in config/settings_data.json and other configuration files because each store has different settings (store names, payment configs, branding, regional preferences, app configurations).

Problematic workflow (before this fix):

# Work on theme improvements in dev branch
git checkout dev
git commit -m "Add new product grid layout to be used across our stores"

# Deploy to first store - conflicts with Shopify's auto-pushed settings
git checkout red-tie-store
git merge dev  # Conflict! Shopify modified store settings

# Manually resolve conflicts, commit
# Results in conflicts requiring manual resolution:
# <<<<<<< HEAD
# {"store_name": "Red Tie Clothing", "announcement_text": "SALE: 50% off winter coats!"}
# =======
# {"store_name": "Dev Store", "announcement_text": "Test announcement"}
# >>>>>>> dev

# Deploy to second store
git checkout blue-dress-store
git merge dev  # Another conflict! Different store settings. Same time-consuming process again

# Deploy to third store
git checkout green-shoes-store
git merge dev # Another conflict! Manually resolve the SAME type of conflicts again. This is getting painful...

# Repeat for every store... Yellow Store, Purple Store, etc.

Users are forced into the complex separate-branch approach because Shopify's GitHub integration pushes store-specific customizations (made by store admins) back to branches, making a unified single-branch workflow impossible. The result: developers must manually resolve the same settings conflicts repeatedly across multiple stores.

These conflicts require manual resolution every time, which is time-consuming and error-prone.

Solution

Custom Git merge drivers that automatically preserve the current branch's settings during merges:

• Custom Merge Driver: Preserves current branch settings for JSON config files
• Selective Application: Only affects settings files, code files merge normally
• Universal: Works for multiple stores, environments, or any branching strategy
• Git-Native: Uses Git's built-in merge driver system

Usage

# Setup (one time required to avoid merge conflicts)
shopify theme git-setup --multi-environment
git add .gitattributes && git commit -m "Add Git merge config" # preserves branch-specific files during merges 
# e.g. red-tie-store keeps it's store name, branding...

# Verify setup:
shopify theme git-setup --status

# Multi-store workflow (Same commands as before)
git checkout main
git commit -m "Add new product grid layout"

git checkout red-tie-store
git merge main  # No conflicts. Red Store settings automatically preserved

git checkout blue-dress-store
git merge main  # No conflicts. Blue Store settings automatically preserved

git checkout green-shoes-store
git merge main  # No conflicts. Green Store settings automatically preserved

# New layout efficiently pushed across all stores

Note: This solution makes the separate-branch approach work smoothly. While users ideally want a single branch for all stores, our solution makes the current multi-branch reality much more manageable by eliminating manual conflict resolution.

Implementation

New Commands:

• shopify theme git-setup --multi-environment - Configure merge strategies
• shopify theme git-setup --status - Check configuration
• shopify theme git-setup --reset - Remove configuration
• shopify theme git-merge-preserve - Internal merge driver

Files:

• git-setup.ts - CLI command for setup
• git-merge-preserve.ts - Git merge driver
• git-config.ts - Git configuration management
• theme-merge.ts - Custom merge logic

Testing

✅ 53 comprehensive tests covering all functionality
✅ Build, lint, and type checking pass
✅ Manual testing with real Git repositories validates merge preservation

Benefits

• Eliminates manual conflict resolution for store settings files
• Preserves store-specific settings automatically during merges
• Enables confident theme deployment without fear of breaking store configurations
• Backwards compatible - only activates when configured
• Git-native solution using standard merge driver functionality

Future Considerations

• Support for additional file types (deployment configs, robots.txt, store policies)
• Store-specific validation rules and deployment workflows
• Integration with multi-store theme management pipelines

[lmcrean]

it's ready @isaacroldan @amcaplan @gonzaloriestra -- any chance of a review please?

[frandiox]

Hi 👋

Thanks so much for your interest in this issue and for the significant effort you've put into this pull request.

While we appreciate the work, the approach proposed here unfortunately doesn't align with the direction we're planning for this area of the project. It's also unfortunate that we can't prioritize this issue at the time but it's already tracked by the team 🙏

Thanks again for all the work!