feat: Add GitHub template support for stack deployments

[martin-helmich]

Summary

Adds support for deploying stacks directly from GitHub template repositories using the new --from-template flag.

This enables users to quickly deploy pre-configured application stacks without manually managing docker-compose files locally. Template names like mittwald/n8n automatically resolve to the corresponding mittwald/stack-template-n8n repository.

What This Enables

Quick Stack Deployment
Deploy popular applications instantly from curated templates:

mw stack deploy --from-template=mittwald/n8n --stack-id=s-abc123

Template Repository Naming
Template names follow a simple convention:

• Input: mittwald/n8n
• Resolves to: github.com/mittwald/stack-template-n8n

Environment Configuration
Templates can include default environment variables via .env files, which can be overridden:

# Use template defaults
mw stack deploy --from-template=mittwald/n8n

# Override with local environment
mw stack deploy --from-template=mittwald/n8n --env-file=./production.env

Environment Variable Priority (from lowest to highest):

1. Template .env file (if present)
2. System environment variables
3. Local --env-file flag

Behavior

• Fetches docker-compose.yml and optional .env from the template repository's main branch
• Mutually exclusive with --compose-file flag (prevents accidental mixing of local and remote sources)
• Clear error messages for common issues (template not found, rate limits, network errors)
• No local caching - always fetches fresh template content

Use Cases

• Quick prototyping: Spin up applications without setup overhead
• Standardized deployments: Teams can share vetted stack configurations via templates
• Easy onboarding: New users can deploy complex stacks with a single command
• Version consistency: Templates ensure everyone uses the same configuration

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR adds support for deploying container stacks directly from GitHub template repositories using a new --from-template flag. Users can now quickly deploy pre-configured applications without managing local docker-compose files.

Changes:

• Introduces template loading functionality with GitHub repository fetching and environment variable handling
• Adds a custom retrieve function to automatically detect single stacks in a project context
• Updates the deploy command to support both local file and template-based deployments

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/lib/resources/stack/template-loader.ts	Core template loading logic with GitHub API integration and error handling
src/lib/resources/stack/template-loader.test.ts	Comprehensive test suite for template loading functionality
src/lib/resources/stack/flags.ts	Adds automatic stack ID retrieval for single-stack projects
src/lib/resources/stack/env.ts	Extends environment handling with prompt and generate placeholders
src/lib/context/FlagSetBuilder.ts	Adds retrieveFunction option to flag set builder
src/commands/stack/deploy.tsx	Integrates template loading into deploy command with new flag
docs/stack.md	Documents the new --from-template flag and its behavior

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