Set User-Agent header for OCI HTTP requests (#478)

* Set User-Agent header for OCI HTTP requests

* IORegistry value is actually a NUL-terminated C string

* Use sysctl instead of IOKit

Sources/tart/DeviceInfo/DeviceInfo.swift

@@ -0,0 +1,37 @@
+import Foundation
+import Sysctl
+
+class DeviceInfo {
+  private static var osMemoized: String? = nil
+  private static var modelMemoized: String? = nil
+
+  static var os: String {
+    if let os = osMemoized {
+      return os
+    }
+
+    osMemoized = getOS()
+
+    return osMemoized!
+  }
+
+  static var model: String {
+    if let model = modelMemoized {
+      return model
+    }
+
+    modelMemoized = getModel()
+
+    return modelMemoized!
+  }
+
+  private static func getOS() -> String {
+    let osVersion = ProcessInfo.processInfo.operatingSystemVersion
+
+    return "macOS \(osVersion.majorVersion).\(osVersion.minorVersion).\(osVersion.patchVersion)"
+  }
+
+  private static func getModel() -> String {
+    return SystemControl().hardware.model
+  }
+}

Sources/tart/OCI/Registry.swift

@@ -387,6 +387,9 @@ class Registry {
       request.addValue(value, forHTTPHeaderField: name)
     }
 
+    request.setValue("Tart/\(CI.version) (\(DeviceInfo.os); \(DeviceInfo.model))",
+                     forHTTPHeaderField: "User-Agent")
+
     return try await Fetcher.fetch(request, viaFile: viaFile)
   }
 }