gh-90300: Fix cmdline.rst (GH-116721)

* Fix the description of the "-b" option.
* Add references to environment variables for "-s" and "-X dev" options.

Doc/using/cmdline.rst

@@ -242,12 +242,13 @@ Miscellaneous options
 
 .. option:: -b
 
-   Issue a warning when comparing :class:`bytes` or :class:`bytearray` with
-   :class:`str` or :class:`bytes` with :class:`int`.  Issue an error when the
-   option is given twice (:option:`!-bb`).
+   Issue a warning when converting :class:`bytes` or :class:`bytearray` to
+   :class:`str` without specifying encoding or comparing :class:`!bytes` or
+   :class:`!bytearray` with :class:`!str` or :class:`!bytes` with :class:`int`.
+   Issue an error when the option is given twice (:option:`!-bb`).
 
    .. versionchanged:: 3.5
-      Affects comparisons of :class:`bytes` with :class:`int`.
+      Affects also comparisons of :class:`bytes` with :class:`int`.
 
 .. option:: -B
 
@@ -386,6 +387,8 @@ Miscellaneous options
    Don't add the :data:`user site-packages directory <site.USER_SITE>` to
    :data:`sys.path`.
 
+   See also :envvar:`PYTHONNOUSERSITE`.
+
    .. seealso::
 
       :pep:`370` -- Per user site-packages directory
@@ -517,7 +520,7 @@ Miscellaneous options
      asyncio'``.  See also :envvar:`PYTHONPROFILEIMPORTTIME`.
    * ``-X dev``: enable :ref:`Python Development Mode <devmode>`, introducing
      additional runtime checks that are too expensive to be enabled by
-     default.
+     default.  See also :envvar:`PYTHONDEVMODE`.
    * ``-X utf8`` enables the :ref:`Python UTF-8 Mode <utf8-mode>`.
      ``-X utf8=0`` explicitly disables :ref:`Python UTF-8 Mode <utf8-mode>`
      (even when it would otherwise activate automatically).

Python/initconfig.c

@@ -142,8 +142,8 @@ static const char usage_line[] =
 /* Lines sorted by option name; keep in sync with usage_envvars* below */
 static const char usage_help[] = "\
 Options (and corresponding environment variables):\n\
--b     : issue warnings about str(bytes_instance), str(bytearray_instance)\n\
-         and comparing bytes/bytearray with str. (-bb: issue errors)\n\
+-b     : issue warnings about converting bytes/bytearray to str and comparing\n\
+         bytes/bytearray with str or bytes with int. (-bb: issue errors)\n\
 -B     : don't write .pyc files on import; also PYTHONDONTWRITEBYTECODE=x\n\
 -c cmd : program passed in as string (terminates option list)\n\
 -d     : turn on parser debugging output (for experts only, only works on\n\