-I need help with this. Supposedly, such a plugin would provide a `formbuilder_setup`
-hook which would add the button, and a cgi hook which would interecept
-"Show Diff" clicks. This would show a diff between
-`titlepage(possibly_foolish_untaint($form->field("page")))`
-and the provided `$form->field("editcontent")`.
-
-But:
-
- * How could the case of concurrent editing be handled ?
- Especially as (I think) only the RCS backend can know that
- this has happened.
- * May I hijack the `page_preview` template variable to show
- my diff output? (the patch below assumes this).
- * Using the formbuilder hook to add a button, and coerce `editpage()`
- into showing the edit form again rather that saving the page needs
- the following patch. (note that this is not the only template which has
- its submit buttons hardcoded; is this supposed to work around something?)
-
-I've got a [preliminary implementation](http://www.jk.fr.eu.org/ikiwiki/showdiff.pm),
-which depends on [this patch](http://www.jk.fr.eu.org/ikiwiki/pluggable_editpage_buttons.diff)
-and the [[plugins/contrib/plaintext]] plugin.
-
-There is still some tweaking needed, though.
-
---[[JeremieKoenig]]
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