Generate list of external files

CHDataManagement/Model/Content+Generation.swift

@@ -12,6 +12,7 @@ extension Content {
             self.copyRequiredFiles()
             self.generateRequiredImages()
             self.results.recalculate()
+            self.generateListOfExternalFiles()
             self.status("Generation completed")
         }
     }
@@ -279,4 +280,27 @@ extension Content {
             return
         }
     }
+
+    // MARK: Additional infos
+
+    private var externalFileListName: String { "external-files.txt" }
+
+    private func generateListOfExternalFiles() {
+        let files = results.requiredFiles
+            .filter { $0.isExternallyStored }
+
+        guard !files.isEmpty else {
+            if storage.hasFileInOutputFolder(externalFileListName) {
+                storage.deleteInOutputFolder(externalFileListName)
+            }
+            return
+        }
+
+        let content = files
+            .map { $0.absoluteUrl }
+            .sorted()
+            .joined(separator: "\n")
+
+        storage.write(content, to: externalFileListName)
+    }
 }