Eli Zaretskii <eliz@gnu.org> writes:

>> +(defvar package-trash-old-packages t
>> +  "If non-nil, `package-delete' may trash packages.
>
> Why "may"?

Since after this patch, `package-delete' may trash packages, or may not,
depending on the value of `delete-by-moving-to-trash'.

>> +`delete-by-moving-to-trash' must be non-nil for this variable to
>> +have an effect.")
>
> I think it would be better to make this defcustom.

Right, I forgot to do that. I updated and attached a new patch.