[duplicate-code] Duplicate Code Analysis Report — difc tag-set mutation methods

[github-actions]

Analysis of commit 16ac464

Summary

This analysis identified 1 significant duplication pattern in the internal/difc/ package: the Label and Capabilities types share nearly identical concurrent tag-set mutation methods backed by the same underlying data structure (map[Tag]struct{} + sync.RWMutex). This results in ~25 duplicated lines across 5 methods.

Detected Patterns

1. Concurrent tag-set methods duplicated between Label and Capabilities — Severity: Medium — See sub-issue [duplicate-code] Duplicate Code Pattern: Concurrent tag-set methods in Label and Capabilities #8772

Overall Impact

• Total Duplicated Lines: ~25 lines (5 methods, repeated verbatim)
• Affected Files: 2 (internal/difc/capabilities.go, internal/difc/labels.go)
• Maintainability Risk: Medium — a bug fix or logging change to one must be manually mirrored to the other
• Refactoring Priority: Low-Medium — the logic is stable and tested, but the duplication grows risk over time

Next Steps

1. Review the individual pattern sub-issue for detailed analysis
2. Consider extracting a generic tagSet type or embedding Label inside Capabilities
3. Evaluate whether Capabilities methods can simply delegate to an inner Label

Analysis Metadata

• Analyzed Files: 1 Go file changed in commit (internal/difc/capabilities.go); cross-referenced with internal/difc/labels.go
• Detection Method: Semantic pattern matching — symbol comparison across internal/difc/
• Commit: 16ac464
• Analysis Date: 2026-07-06