Fix exception of groupOptionAmbiguityError

Author: moh-hassan

src/CommandLine/Error.cs

@@ -584,8 +584,12 @@ public bool Equals(MissingGroupOptionError other)
 
     public sealed class GroupOptionAmbiguityError : NamedError
     {
+        public NameInfo Option;
+
         internal GroupOptionAmbiguityError(NameInfo option)
             : base(ErrorType.GroupOptionAmbiguityError, option)
-        { }
+        {
+            Option = option;
+        }
     }
 }

src/CommandLine/Text/SentenceBuilder.cs

@@ -158,6 +158,9 @@ public override Func<Error, string> FormatError
                                         "' (",
                                         string.Join(", ", missingGroupOptionError.Names.Select(n => n.NameText)),
                                         ") is required.");
+                                case ErrorType.GroupOptionAmbiguityError:
+                                    var groupOptionAmbiguityError = (GroupOptionAmbiguityError)error;
+                                    return "Both SetName and Group are not allowed in option: (".JoinTo(groupOptionAmbiguityError.Option.NameText, ")");
                             }
                             throw new InvalidOperationException();
                         };