Re: Comment in verilog-mode.el about supported versions

[wsnyder@wsnyder.org (Wilson Snyder)]

>On Mon, 19 Dec 2016, Wilson Snyder wrote:
>
>>
>>>> On Mon, Dec 19, 2016, 5:19 PM Tino Calancha <tino.calancha@gmail.com> wrote:
>>>>>
>>>>> in the comentary of
>>>>> lisp/progmodes/verilog-mode.el
>>>>> you can find following comment:
>>>>> ;;    This code supports Emacs 21.1 and later
>>>>> ;;    And XEmacs 21.1 and later
>>>>> ;;    Please do not make changes that break Emacs 21.  Thanks!
>>>>>
>>>>> I could understand this comment in a version of this file
>>>>> elsewhere, e.g. ELPA, but not in the built-in version in Emacs.
>>>>> Why is this comment needed?
>>>>> Is it OK to drop from the master branch this kind of comments?
>>
>> Please retain this, this entire file is identical with that
>> used on other versions of Emacs. It would be otherwise
>> be nearly impossible to manage diverging files.
>Sorry, I don't understand why it should be difficult or what makes more 
>difficult to handle this file that, for instance tramp or cc-mode.
>
>Wouldn't it better to keep one verilog-mode.el version in ELPA 
>fully compatible with Emacs-21?
>And let the file in the master branch to benefit of all that
>has come since Emacs-21?
>
>I also notice that the file is very large (> 14 klines).
>Maybe it would be easier to maintain if the file is split in 4-5 files.

Verilog-mode is a bit unique.  It's not just a programming
mode that is used inside Emacs, but a computer aided design
tool that extends the Verilog language, relied on in most
every chip design company, and often run as a standalone
tool from Emacs batch.

Thus there are often important bugs which need to be fixed
back into what would otherwise be considered "old" Emacs
versions. cc-mode and like doesn't have this issue.

Also because of this, verilog-mode.el is often part of the
source code control system of design environments, which
need to run regardless that different users and systems may
have different Emacs versions installed.

Users often upgrade verilog-mode.el themselves, and so
having a single file, that they can easily install and know
will work, no matter their version of Emacs, is critical.

Perhaps this path is more development work (though due to
version maintenance effort I'd argue that). But, I don't see
any way in which splitting versions nor splitting files
would help the users.

Anyhow, regardless of these choices, new Emacs features are
made available.  By no means is the least common denominator
all that is supported.

-Wilson