Hello Drew,

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

> My code includes just a vacuous defvar, to
> declare the var but not initialize it to nil.
>
>   (defvar Info-minibuf-history)

You should not have to do this, this defvar should be in info.el on top
of file ideally.  Initialized to nil or not I don't know, but it should
be declared anyway.
I personally initialize these history vars to nil in all my packages. 

> That works, and in all Emacs versions, AFAIK.

AFAIK this variable is not used in previous emacs versions.

-- 
Thierry