Add Git Hosting Provider abstraction layer (Issue #902)

[konard]

Summary

Implements a Git Hosting Provider abstraction layer to support multiple git hosting platforms (GitHub, GitLab, BitBucket) through a unified interface.

Fixes #902

Features

• Abstract GitHostingProvider base class defining the interface all providers must implement
• Full GitHubProvider implementation using gh CLI with all methods working
• Stub implementations for GitLabProvider (glab CLI) and BitBucketProvider (REST API)
• Provider detection based on URL patterns with priority-based matching
• Provider registry for managing and extending providers
• URL parsing and normalization for all providers (handles different formats)
• CLI tool preference with API fallback support built into the architecture

Architecture

File	Description
src/git-hosting/provider.interface.mjs	Abstract base class with JSDoc types
src/git-hosting/github.provider.mjs	Full GitHub implementation using gh CLI
src/git-hosting/gitlab.provider.mjs	GitLab stub (uses glab CLI)
src/git-hosting/bitbucket.provider.mjs	BitBucket stub (REST API)
src/git-hosting/index.mjs	Factory, registry, and exports
tests/test-git-hosting-providers.mjs	74 comprehensive tests

Key Methods in Provider Interface

// Provider information
getProviderInfo()           // Returns name, displayName, hostname, cliTool, etc.

// URL handling
isProviderUrl(url)          // Check if URL belongs to this provider
parseUrl(url)               // Parse URL into owner, repo, type, number, etc.
normalizeUrl(url)           // Convert any URL format to canonical HTTPS
buildUrl(options)           // Build URL from components

// Authentication
checkAuth()                 // Verify CLI/API authentication status
checkCliAvailable()         // Check if CLI tool is installed

// API operations (GitHub fully implemented, others stubbed)
getIssue(owner, repo, number)
getPullRequest(owner, repo, number)
createPullRequest(owner, repo, options)
getRepositoryInfo(owner, repo)

Usage Example

import { 
  detectProvider, 
  getProviderForUrl, 
  getProvider 
} from './src/git-hosting/index.mjs';

// Detect provider from URL
const info = detectProvider('https://gitlab.com/owner/repo/-/issues/123');
// { name: 'gitlab', hostname: 'gitlab.com' }

// Get provider instance for URL
const provider = getProviderForUrl('https://github.com/owner/repo');
const parsed = provider.parseUrl('https://github.com/owner/repo/issues/42');
// { valid: true, type: 'issue', owner: 'owner', repo: 'repo', number: 42 }

// Get provider by name
const github = getProvider('github');
const issue = await github.getIssue('owner', 'repo', 123);

Test Results

📊 Test Results: 74/74 passed
✅ All tests passed!

Tests cover:

• Provider detection for all three providers
• URL parsing (issues, PRs/MRs, repos, users)
• URL building and normalization
• Provider info retrieval
• Rate limit error detection
• Edge cases (invalid URLs, null inputs, etc.)

ESLint Configuration Update

Updated eslint.config.mjs to add argsIgnorePattern: '^_' for the no-unused-vars rule. This allows underscore-prefixed parameters in abstract methods and stub implementations, which is a standard pattern for intentionally unused parameters.

Next Steps (Future PRs)

1. Complete GitLab and BitBucket provider implementations
2. Migrate existing github.lib.mjs to use GitHubProvider
3. Add self-hosted provider support (GitHub Enterprise, GitLab self-hosted)

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[konard]

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