Fixed: Don't import duplicate NFO extra files

Co-Authored-By: Mark McDowall <markus101@users.noreply.github.com>

src/NzbDrone.Core/Extras/ExtraService.cs

@@ -74,9 +74,28 @@ namespace NzbDrone.Core.Extras
                                                                      .Select(e => e.Trim(' ', '.'))
                                                                      .ToList();
 
-            var matchingFilenames = files.Where(f => Path.GetFileNameWithoutExtension(f).StartsWith(sourceFileName, StringComparison.InvariantCultureIgnoreCase));
+            var matchingFilenames = files.Where(f => Path.GetFileNameWithoutExtension(f).StartsWith(sourceFileName, StringComparison.InvariantCultureIgnoreCase)).ToList();
+            var filteredFilenames = new List<string>();
+            var hasNfo = false;
 
             foreach (var matchingFilename in matchingFilenames)
+            {
+                // Filter out duplicate NFO files
+
+                if (matchingFilename.EndsWith(".nfo", StringComparison.InvariantCultureIgnoreCase))
+                {
+                    if (hasNfo)
+                    {
+                        continue;
+                    }
+
+                    hasNfo = true;
+                }
+
+                filteredFilenames.Add(matchingFilename);
+            }
+
+            foreach (var matchingFilename in filteredFilenames)
             {
                 var matchingExtension = wantedExtensions.FirstOrDefault(e => matchingFilename.EndsWith(e));