Attach recorded snapshot (pointfreeco#586)

Author: marcelofabri

Sources/SnapshotTesting/AssertSnapshot.swift

@@ -235,6 +235,15 @@ public func verifySnapshot<Value, Format>(
 
       guard !recording, fileManager.fileExists(atPath: snapshotFileUrl.path) else {
         try snapshotting.diffing.toData(diffable).write(to: snapshotFileUrl)
+        #if !os(Linux) && !os(Windows)
+        if ProcessInfo.processInfo.environment.keys.contains("__XCODE_BUILT_PRODUCTS_DIR_PATHS") {
+          XCTContext.runActivity(named: "Attached Recorded Snapshot") { activity in
+            let attachment = XCTAttachment(contentsOfFile: snapshotFileUrl)
+            activity.add(attachment)
+          }
+        }
+        #endif
+
         return recording
           ? """
             Record mode is on. Turn record mode off and re-run "\(testName)" to test against the newly-recorded snapshot.