Fix missmatch option name in tester

For eng/ide/ada_language_server#1314

Author: Boulanger

source/tester/tester-run.adb

@@ -51,7 +51,7 @@ procedure Tester.Run is
 
       Output_Format : constant VSS.Command_Line.Value_Option :=
         (Short_Name  => "",
-         Long_Name   => "output-format",
+         Long_Name   => "format",
          Value_Name  => "output_format_option",
          Description =>
            VSS.Strings.Conversions.To_Virtual_String

source/tester/tester-tests.adb

@@ -1259,15 +1259,19 @@ package body Tester.Tests is
          Text.Append ("Recent output from server:");
          Text.Append (GNATCOLL.JSON.Write (Output, False));
 
-      else --  Default behaviour is "diff"
+      else
+         if On_Failed_Val /= "diff" then
+            Text.Append
+              ("Unrecognized value for Format: reverting to ""diff""");
+         end if;
          declare
             Diff : Unbounded_String;
          begin
             Diff := Generate_Diff
               (Left    => Output,
                Right   => Waits,
                Indent  => 0,
-               Minimal => True);
+               Minimal => False);
             Text.Append ("Diff:");
             Text.Append (To_String (Diff));
          end;