In upgrading to version 2.1.0-rc1 I'm getting the following error when attemting
to access the CMS:

Fatal error: Call to undefined method stdClass::allMethodNames() in /var/www/html/w/sapphire/core/Object.php on line 203

After many hours of playing with the upgrading, Upgrading one table at a
time. It seems to be a problem with the SiteTree table and the CMS.
the CMS does not like the first record of SiteTree to be of className="HomePage"

mysite/templates/HomePage.ss and mysite/code/HomePage.php
are not the problem because I can copy the Page.ss and Page.php
to HomePage.ss and HomePage.php and have the same problem.

The Record in SiteTree is record ID=1
If I change the first record to className="Page" it works
UPDATE SiteTree set className="Page" where ID=1;
If I change a non-first record to className="HomePage" it works
UPDATE SiteTree set className="HomePage" where ID=5;
However if I try to change the first record ID to another value
where it remains the first record it errors out again
UPDATE SiteTree set className="HomePage",ID=2 where ID=1;
I can change the className to another class (custom) and it works
UPDATE SiteTree set className="SectionHolder" where ID=1;
I can change the ID to a higher unused value (ID=6 where ID=3 and
ID=4) and it still errors
UPDATE SiteTree set className="HomePage",ID=6 where ID=1;

Playing with the differences the problem appears that
you need a getCMSFields function even if there are no
data fields.

Actually, that didn't work either. I was accidently going
back to a version that className was still set to "Page";

Yes
I pretty much do a db/build?flush=1 whenever I change the code/*.php
files