chore: import upstream snapshot with attribution

Sources/Containerization/AttachedFilesystem.swift

@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+// Copyright © 2025-2026 Apple Inc. and the Containerization project authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//===----------------------------------------------------------------------===//
+
+import ContainerizationExtras
+import ContainerizationOCI
+
+/// A filesystem that was attached and able to be mounted inside the runtime environment.
+public struct AttachedFilesystem: Sendable {
+    /// The type of the filesystem.
+    public var type: String
+    /// The path to the filesystem within a sandbox.
+    public var source: String
+    /// Destination when mounting the filesystem inside a sandbox.
+    public var destination: String
+    /// The options to use when mounting the filesystem.
+    public var options: [String]
+
+    public init(mount: Mount, allocator: any AddressAllocator<Character>) throws {
+        switch mount.runtimeOptions {
+        case .virtiofs:
+            let name = try hashFilePath(path: mount.source)
+            self.source = name
+        case .virtioblk:
+            let char = try allocator.allocate()
+            self.source = "/dev/vd\(char)"
+        case .shared, .any:
+            self.source = mount.source
+        }
+        self.type = mount.type
+        self.options = mount.options
+        self.destination = mount.destination
+    }
+
+    public init(type: String, source: String, destination: String, options: [String]) {
+        self.type = type
+        self.source = source
+        self.destination = destination
+        self.options = options
+    }
+}