WIP: Add Plugin Architecture for Extensible CLI

[eciuca]

Summary

This PR introduces a plugin architecture that allows extending Backlog CLI with additional commands without modifying the core codebase. The implementation follows the git plugin pattern (similar to git-lfs, git-flow, etc.).

What's Changed

Core Changes

• Plugin Router: Added src/core/plugin-router.ts to handle plugin discovery and execution
• CLI Integration: Modified src/cli.ts to route unknown commands to plugins
• Type System: Extended Task type with index signature to allow plugins to add custom fields
• Parser Enhancement: Updated markdown parser to preserve custom fields from plugins

Documentation

• Plugin Guide: Added comprehensive docs/plugins.md with:
  • How plugins work
  • Installation and usage instructions
  • Plugin development guide with examples
  • Best practices

Task Definitions

Added task documentation for the implementation:

• TASK-298: Plugin routing system
• TASK-299: Adapter pattern for plugin integration
• TASK-300: Generic type support for plugins

How It Works

1. Plugin Discovery: When running backlog <command>, CLI checks if it's a core command
2. Plugin Routing: If not found, looks for backlog-<command> executable in PATH or node_modules/.bin
3. Plugin Execution: Executes the plugin and forwards output directly to terminal

Example Usage

# Install a plugin globally
npm install -g backlog-jira

# Use the plugin
backlog jira sync
backlog jira push task-123

Design Principles

• Zero Core Changes: Plugins don't require modifying core code
• Zero Coupling: Plugins interact via CLI interface, not internal APIs
• Backward Compatible: All existing functionality remains unchanged
• Simple & Familiar: Follows git plugin pattern that developers already know

Example Plugin

A working implementation is available at:
https://github.com/eciuca/Backlog.md-jira-plugin

This Jira integration plugin demonstrates:

• Bidirectional sync with Jira
• Custom field storage (jiraKey, jiraStatus, etc.)
• Independent deployment and versioning
• Zero modifications to core Backlog.md

Benefits

1. Extensibility: Add new integrations without touching core
2. Maintainability: Plugins are independently maintained and versioned
3. Community: Enables community-contributed integrations
4. Clean Core: Keeps core focused on task management

Testing

The plugin architecture has been tested with the Jira plugin implementation, including:

• Plugin discovery and routing
• Custom field persistence
• CLI command forwarding
• Error handling

Related

• Plugin implementation example: https://github.com/eciuca/Backlog.md-jira-plugin
• Task definitions: TASK-298, TASK-299, TASK-300

[MrLesk]

Hi @eciuca
PR looks good from a quick check. I am finishing the implementation of the MCP integration and will check your PR in detail as soon as possible

[eciuca]

I updated as WIP as I need to make sure it integrates correctly with plugin commands. And to test it some more on the projects I work on

[mindofjonas]

Any update on this one? Was looking to create a plugin to embedded Excalidraw diagrams into docs/tasks