Problem with CUSTOM_ID persistence during exporting

[Bernt Hansen <bernt@norang.ca>]

Hi Carsten,

I noticed a problem with custom ids that should probably be fixed.

I was playing with a temporary custom id for a document - so I added it
and exported.  Then when I removed the id it's still there.  The
org-export-preferred-target-alist still has the mapping of section
number to preferred id which I removed.  I think it also applies to
different documents.

I think the variables

(defvar org-export-target-aliases nil
  "Alist of targets with invisible aliases.")
(defvar org-export-preferred-target-alist nil
  "Alist of section id's with preferred aliases.")
(defvar org-export-code-refs nil
  "Alist of code references and line numbers")

should probably all be set to nil before export processing of any file.
These collect values during the export process which affects future
exports.

I think it's possible to set a CUSTOM_ID is section 1 on document X and
have it apply to document Y if you export document Y after document X.

This just feels wrong to me.

All export functions should probably call some org-exp-init function to
clear these (and maybe other vars) using during the export process.

What do you think?

-Bernt