_pytest/config.py: In --help, show args with `=` instead of space.

The `=` is better because it encourages folks to use the form that doesn't
suffer from issue #436 (https://bitbucket.org/hpk42/pytest/issue/436), which
can cause the arg to be treated as an "anchor" and used as the (unexpected)
path for searching for conftest.py files.

--HG--
branch : help_show_args_with_equals_instead_of_space

_pytest/config.py

@@ -436,7 +436,7 @@ class DropShorterLongHelpFormatter(py.std.argparse.HelpFormatter):
             if len(option) == 2 or option[2] == ' ':
                 return_list.append(option)
             if option[2:] == short_long.get(option.replace('-', '')):
-                return_list.append(option)
+                return_list.append(option.replace(' ', '='))
         action._formatted_action_invocation = ', '.join(return_list)
         return action._formatted_action_invocation