patch 8.2.0293: various Ex commands not sufficiently tested

Problem:    Various Ex commands not sufficiently tested.
Solution:   Add more test cases. (Yegappan Lakshmanan, closes #5673)
diff --git a/src/testdir/test_plus_arg_edit.vim b/src/testdir/test_plus_arg_edit.vim
index 64533e7..c52044d 100644
--- a/src/testdir/test_plus_arg_edit.vim
+++ b/src/testdir/test_plus_arg_edit.vim
@@ -18,7 +18,7 @@
   e! ++enc=utf8 Xfile
   call assert_equal('[?][?][???][??]', getline(1))
 
-  e! ++enc=utf8 ++bad=_ Xfile
+  e! ++encoding=utf8 ++bad=_ Xfile
   call assert_equal('[_][_][___][__]', getline(1))
 
   e! ++enc=utf8 ++bad=drop Xfile