Preview deployments — deploy each git branch to a unique URL

[aynaash]

Summary

Implement preview deployments so each git branch/PR gets its own unique URL, similar to Vercel's preview system.

Expected Behavior

# On branch "feature/new-homepage"
nextdeploy ship --preview

# Deploys to: feature-new-homepage.myapp.nextdeploy.app
# Or: preview-abc123.d1234.cloudfront.net

Design Options

1. Lambda aliases — Create a Lambda alias per branch, route via CloudFront behavior
2. Separate Lambda functions — <app>-preview-<branch> with separate Function URLs
3. Path-based — Single Lambda with branch routing via header/path

Required Components

• Branch name detection from git
• Unique subdomain or path generation
• Separate S3 prefix for preview assets
• Cleanup mechanism for stale previews

Commands

nextdeploy ship --preview          # Deploy current branch as preview
nextdeploy preview list            # List active previews
nextdeploy preview delete <branch> # Delete a preview

Difficulty: Hard · Language: Go