Answer architecture round 2: one folder walk and one sorted-keys helper, REGENERATE for the index, and the held decisions naming the items that end them

shipped_test.go

@@ -39,13 +39,13 @@ func loadedCategories(f *Generator) []string {
 	return out
 }
 
-// REPIN=1 rewrites the index.
+// REGENERATE=1, which go generate sets, rewrites the index.
 func TestShippedIndexIsCurrent(t *testing.T) {
 	got, err := shippedIndexSource(newShippedWhole(t))
 	if err != nil {
 		t.Fatal(err)
 	}
-	if os.Getenv("REPIN") == "1" {
+	if os.Getenv("REGENERATE") == "1" {
 		if err := os.WriteFile(shippedIndexFile, got, 0o644); err != nil {
 			t.Fatal(err)
 		}