Summary

This PR creates a new reusable composite action for retrieving changed files and refactors two existing actions to use it, eliminating duplicate code and improving security.

Changes

1. New Get-Changed-Files Action

• Created .github/actions/infrastructure/get-changed-files/ composite action
• Supports both pull_request and push events
• Optional filtering by file pattern (e.g., *.md, .github/)
• Full pagination support - fetches ALL changed files (no 100-file limit)
• Returns JSON array of file paths for easy consumption
• Includes comprehensive README with usage examples

2. Refactored Markdownlinks Action

• Now uses get-changed-files with ilter: '*.md'
• Reduced from 108 lines 77 lines (29% reduction)
• Eliminated 31 lines of duplicate file retrieval code
• Uses secure environment variable instead of direct string interpolation

3. Refactored Path-Filters Action

• Now uses get-changed-files for PR events
• Reduced from 130 lines 123 lines
• Eliminated 15+ lines of duplicate pagination logic
• Fixed JSON security issue: now uses romJSON() instead of unsafe JSON.parse()
• Added detailed logging for filter analysis
• Proper escaping prevents potential code injection from filenames

Benefits

Code Reuse: Eliminates ~60 lines of duplicate code across actions
Maintainability: Centralizes file retrieval logic in one place - future changes only need to be made once
Security: Fixes JSON injection vulnerability in path-filters
Consistency: All actions using changed files will behave identically
Completeness: Full pagination ensures no files are missed in large PRs
Clarity: Better logging and documentation

Testing

• YAML syntax validated
• No linting errors
• All actions maintain backward compatibility
• Changes follow existing patterns in the codebase

Related

This is part of splitting up PR #26350 into smaller, more manageable chunks. This PR contains the foundation (reusable action) and refactoring work, while the merge conflict checker will come in a separate PR.