bug#1118: 23.0.60; Info claims no index exists if first instance of an info file is visited via info-lookup-symbol

[Juri Linkov <juri@jurta.org>]

>  > emacs -Q
>  > C-h S add-text-properties RET ; use info-look to find 
> add-text-properties
>  > C-x b *info* RET              ; switch to info buffer
>  > i                             ; try to lookup something in the index
>  >
>  > complains "No index"
> 
> FWIW, it's due to this change
> 
> 2008-06-15  Juri Linkov  <juri@jurta.org>
> 
>     * info.el (Info-toc): Call Info-toc-nodes instead of Info-build-toc.
>     (Info-toc, Info-insert-toc): Increment nth's index to add PARENT
>     as the second element.
>     (Info-build-toc): Add PARENT element extracted from the Up pointer.
>     Don't print progress messages.
>     (Info-toc-nodes): New variable and function.
>     (Info-index-nodes): Optimize non-string file name case.
>     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>     
> Juri, please have a look.

This whole change was not intended to work with the workflow of `C-h S'.
The problem is that `Info-build-toc' calls `Info-index-node' on the
temporary buffer where it fails to build the index.  Adding a line
`(Info-index-node "Top" file)' at the beginning of `Info-build-toc'
just before `with-temp-buffer' will fix this bug by building the
index outside of the temporary buffer, but I'd like to find
more elegant solution.

-- 
Juri Linkov
http://www.jurta.org/emacs/