Allow relative paths in configuration file

Sources/Generator/Extensions/URL+Extensions.swift

@@ -50,4 +50,23 @@ extension URL {
         let attributes = try? FileManager.default.attributesOfItem(atPath: path)
         return (attributes?[.size] as? NSNumber)?.intValue
     }
+
+    func resolvingFolderTraversal() -> URL? {
+        var components = [String]()
+        absoluteString.components(separatedBy: "/").forEach { part in
+            if part == ".." {
+                if !components.isEmpty {
+                    _ = components.dropLast()
+                } else {
+                    components.append("..")
+                }
+                return
+            }
+            if part == "." {
+                return
+            }
+            components.append(part)
+        }
+        return URL(string: components.joined(separator: "/"))
+    }
 }

Sources/Generator/Files/Configuration.swift

@@ -31,12 +31,12 @@ struct Configuration: Codable {
     /**
      The path to the directory where the root element metadata is located.
      */
-    let contentPath: String
+    var contentPath: String
 
     /**
      The path where the generated website should be written.
      */
-    let outputPath: String
+    var outputPath: String
 
     /**
      Create .md files for content pages, if they don't exist.
@@ -62,6 +62,15 @@ struct Configuration: Codable {
         .init(fileURLWithPath: outputPath)
     }
 
+    mutating func adjustPathsRelative(to folder: URL) {
+        if !contentPath.hasPrefix("/") {
+            contentPath = folder.appendingPathComponent(contentPath).resolvingFolderTraversal()!.path
+        }
+        if !outputPath.hasPrefix("/") {
+            outputPath = folder.appendingPathComponent(outputPath).resolvingFolderTraversal()!.path
+        }
+    }
+
     func printOverview() {
         print("         Source folder: \(contentDirectory.path)")
         print("         Output folder: \(outputDirectory.path)")

Sources/Generator/run.swift

@@ -18,10 +18,11 @@ private func loadConfiguration(at configPath: String) -> Configuration? {
     print("                                                    ")
     print("    Configuration file: \(configPath)")
     let configUrl = URL(fileURLWithPath: configPath)
-    let config: Configuration
+    var config: Configuration
     do {
         let data = try Data(contentsOf: configUrl)
         config = try JSONDecoder().decode(from: data)
+        config.adjustPathsRelative(to: configUrl.deletingLastPathComponent())
     } catch {
         print("   Configuration error: \(error)")
         return nil