[commands] Change signature convention to use POSIX standards.

discord/ext/commands/formatter.py

@@ -149,13 +149,18 @@ class HelpFormatter:
         params = cmd.clean_params
         if len(params) > 0:
             for name, param in params.items():
-                cleaned_name = name.replace('_', '-')
                 if param.default is not param.empty:
-                    result.append('{0}={1}'.format(cleaned_name, param.default))
+                    # We don't want None or '' to trigger the [name=value] case and instead it should
+                    # do [name] since [name=None] or [name=] are not exactly useful for the user.
+                    should_print = param.default if isinstance(param.default, str) else param.default is not None
+                    if should_print:
+                        result.append('[{}={}]'.format(name, param.default))
+                    else:
+                        result.append('[{}]'.format(name))
                 elif param.kind == param.VAR_POSITIONAL:
-                    result.append(cleaned_name + '...')
+                    result.append('[{}...]'.format(name))
                 else:
-                    result.append(cleaned_name)
+                    result.append('<{}>'.format(name))
 
         return ' '.join(result)