added files and started yaml parsing

Package.resolved

@@ -1,6 +1,15 @@
 {
   "object": {
     "pins": [
+      {
+        "package": "Files",
+        "repositoryURL": "https://github.com/JohnSundell/Files",
+        "state": {
+          "branch": null,
+          "revision": "22fe84797d499ffca911ccd896b34efaf06a50b9",
+          "version": "4.1.1"
+        }
+      },
       {
         "package": "Yams",
         "repositoryURL": "https://github.com/jpsim/Yams.git",

Package.swift

@@ -6,14 +6,15 @@ import PackageDescription
 let package = Package(
     name: "Downstream",
     dependencies: [
-      .package(url: "https://github.com/jpsim/Yams.git", from: "4.0.0")
+      .package(url: "https://github.com/jpsim/Yams.git", from: "4.0.0"),
+      .package(url: "https://github.com/JohnSundell/Files", from: "4.0.0")
     ],
     targets: [
         // Targets are the basic building blocks of a package. A target can define a module or a test suite.
         // Targets can depend on other targets in this package, and on products in packages this package depends on.
         .target(
             name: "Downstream",
-            dependencies: ["Yams"]),
+            dependencies: ["Yams", "Files"]),
         .testTarget(
             name: "DownstreamTests",
             dependencies: ["Downstream"]),

Sources/Downstream/downstream.yml

@@ -0,0 +1,2 @@
+associations:
+  main.swift: https://github.com/JohnSundell/Files/blob/master/Sources/Files.swift

Sources/Downstream/main.swift

@@ -6,6 +6,7 @@
 //
 
 import Yams
+import Files
 
 let yaml = """
 associations:
@@ -17,5 +18,22 @@ associations:
 let decoder = YAMLDecoder()
 let associations = try! decoder.decode(AssociationsFile.self, from: yaml)
 
-print(associations)
+//print(associations)
 
+let fileList = CommandLine.arguments[1...]
+let todos = fileList.compactMap { filePath -> String? in
+  let changedFile = try! File(path: filePath)
+
+  if
+    let parent = changedFile.parent,
+    let downsteamYML = try? parent.file(named: "downstream.yml").read(),
+    let associationsFile = try? decoder.decode(AssociationsFile.self, from: downsteamYML)
+  {
+    let fileName = changedFile.path(relativeTo: parent)
+    return associationsFile.associations[fileName]
+  }
+
+  return nil
+}
+
+print(todos)