Check for unused files in output folder

CHDataManagement/Generator/Results/GenerationResults.swift

@@ -46,6 +46,12 @@ final class GenerationResults: ObservableObject {
     @Published
     var emptyPages: Set<LocalizedPageId> = []
 
+    @Published
+    var outputFiles: Set<String> = []
+
+    @Published
+    var unusedFilesInOutput: Set<String> = []
+
     /**
      The url redirects to install to prevent broken links.
 
@@ -114,6 +120,8 @@ final class GenerationResults: ObservableObject {
             self.unsavedOutputFiles = []
             self.emptyPages = []
             self.redirects = [:]
+            self.outputFiles = []
+            self.unusedFilesInOutput = []
         }
         for result in cache.values {
             result.reset()
@@ -229,6 +237,15 @@ final class GenerationResults: ObservableObject {
     func redirect(from originalUrl: String, to newUrl: String) {
         update { self.redirects[originalUrl] = newUrl }
     }
+
+    func created(outputFile: String) {
+        update { self.outputFiles.insert(outputFile.withLeadingSlashRemoved) }
+    }
+
+    func determineFiles(unusedIn existingFiles: Set<String>) {
+        let unused = existingFiles.subtracting(outputFiles)
+        update { self.unusedFilesInOutput = unused }
+    }
 }
 
 private extension Dictionary where Value == Set<LocalizedItemId> {