[romdev]

Finding and eliminating duplicates is a very common software problem that is rarely solved in a reusable, user-friendly way that preserves history while eliminating redundant data. In fact, in 40 years of working with computers I can't think of a single UI that I'd want to emulate.

[Terr_]

Ultimately the key is the business-modeling that captures "duplicates" as Things That Happen.

That's the precondition for any sane UI, and sometimes it's not even obvious because the "duplication" has been transformed, reified into its own concept.