Fix deleting cached files when setting has been enabled (#645)

* Fix deleting cached files when setting has been enabled

* Replace `string=""` with `string.IsNullOrEmpty()`

* Add file caching before delete

* Improve `Apply` and `Revert` mechanism for `KeepChanges`

Author: MahBoiDeveloper

DTAConfig/Settings/FileSourceDestinationInfo.cs

@@ -102,14 +102,12 @@ public void Apply()
                 case FileOperationOption.KeepChanges:
                     if (!File.Exists(DestinationPath))
                     {
-                        SafePath.GetDirectory(Path.GetDirectoryName(CachedPath)).Create();
-
-                        if (!File.Exists(CachedPath))
-                            File.Copy(SourcePath, CachedPath, true);
+                        if (File.Exists(CachedPath))
+                            File.Move(CachedPath, DestinationPath);
+                        else
+                            File.Copy(SourcePath, DestinationPath, true);
                     }
 
-                    FileHelper.CreateHardLinkFromSource(CachedPath, DestinationPath, fallback: true);
-
                     break;
 
                 case FileOperationOption.AlwaysOverwrite:
@@ -139,13 +137,10 @@ public void Revert()
                 case FileOperationOption.KeepChanges:
                     if (File.Exists(DestinationPath))
                     {
-                        string cacheHash = Utilities.CalculateSHA1ForFile(CachedPath);
-                        string destinationHash = Utilities.CalculateSHA1ForFile(DestinationPath);
-
-                        if (cacheHash != destinationHash)
-                            File.Copy(DestinationPath, CachedPath, true);
+                        if (!File.Exists(Path.GetDirectoryName(CachedPath)))
+                            SafePath.GetDirectory(Path.GetDirectoryName(CachedPath)).Create();
 
-                        File.Delete(DestinationPath);
+                        File.Move(DestinationPath, CachedPath);
                     }
                     break;