When the "History" of a page is requested in order to
perform a diff, the pageinfo.php file is used. However
when the diff is requested, a diff on HomePage is
performed regardless of the page whose History is being
This seems to be due to the pageinfo page not including
a pagename field. This problem could occur because I
have set USE_PATH_INFO to be false.
The attached patch adds a pagename field to pageinfo,
and while it might not be the correct solution it at
least seems to work on my installation.