bug#3566: 23.0.94; explain why not to use group defined by define-minor-mode

[Lars Ingebrigtsen]

"Drew Adams" <drew.adams@oracle.com> writes:

> In the Elisp manual and in the doc string for define-minor-mode, we
> are told not to use the custom group that is automatically defined for
> the mode variable, unless we have explicitly used defgroup to define
> the group.
>
> Why? Please provide some explanation.

This is the last change to that part:

 :group GROUP   Custom group name to use in all generated `defcustom' forms.
                Defaults to MODE without the possible trailing \"-mode\".
-               (This default may not be a valid customization group defined
-               with `defgroup'.  Make sure it is.)
+               Don't use this default group name unless you have written a
+               `defgroup' to define that group properly.

The previous version may have been clearer?  I think what it's trying to
say is that if you have a :group, then you should make sure to add a
defgroup to that symbol.

> Why is it inadvisable to use the same generated group for other
> defcustoms without explicitly defining the group? What negative
> consequences arise if that is attempted? Please explain in the doc.

Presumably this is because there are things in a defgroup that should be
there, but aren't if you don't use a defgroup?  I.e., :link and a name
for the group.

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