bug#48058: tab-width's docstring

[Stefan Kangas <stefan@marxist.se>]

Eli Zaretskii <eliz@gnu.org> writes:

>> I didn't expect anything different to happen.  It is just that
>> `tab-width' is determining more than just the "display width of the TAB
>> character": if you (or the major-mode for you) are indenting with spaces
>> the content of the buffer is different according to `tab-width', it not
>> just a matter of "display".
>>
>> But I see your point, and perhaps the docstring is clearer to someone
>> more seasoned than myself, and avoids other pitfalls along the way which
>> I do not even see.  Hopefully, it will feel just as clear to me someday.
>> ;-)
>
> Fair enough, let's see if there are other opinions about this.

I agree that the docstring is somewhat confusing, as it seems to rule
out that this variable is ever used to control indentation.  But some
major modes do precisely that.

Perhaps we could change the docstring note along the lines of:

    NOTE: Some major modes use this variable to determine an indentation
    step, but Emacs itself only uses this to display the width of a TAB
    character.

Would something like that make sense?

---

Also the last line of the docstring is odd to me:

    This should be an integer greater than zero.

Should the "should" be changed to "must"?