An Overlay Is a Layer, Not a Diff

There is a good argument going on in the OpenAPI Overlay repository this week, and I want to take part in it properly rather than with a thumbs-up. Discussion #412, “Overlays: Our purpose is for understanding change,” makes the case that the Overlay Specification’s stated purpose, “to repeatably apply transformations to one or many OpenAPI descriptions,” undersells it. The author’s point is that if all you want is a repeatable transformation, a script is extensible, testable and well understood, and does the job better.