Bug in elide-head

[Matthias Meulien <meulien@club.lemonde.fr>]

Hi,

I think there is a bug in `elide-head'. 

Look at the way the header is made invisible:

(overlay-put elide-head-overlay 'invisible t)

Now suppose you call `elide-head' in a new buffer in `outline-mode';
`outline-mode' had add (outline . t) to `buffer-invisibility-spec', which
made `buffer-invisibility-spec' into a list. But

,----[ C-h v buffer-invisibility-spec RET ]
| (...)
| This variable is always local in all buffers.
| The default is t, which means that text is invisible
| if it has a non-nil `invisible' property.
| If the value is a list, a text character is invisible if its `invisible'
| property is an element in that list.
| If an element is a cons cell of the form (PROP . ELLIPSIS),
| then characters with property value PROP are invisible,
| and they have an ellipsis as well if ELLIPSIS is non-nil.
`----

The header will not disappear because the `invisible' property of the
elide-head-overlay isn't an element of `buffer-invisibility-spec' !
-- 
Matthias