You can clone with
HTTPS or Subversion.
i noticed, when i upgraded to 2.0-b1 and have the scripts within the opcache of php5.5 there occur problems due to invalid cached files.
the cache itself seems not detect correctly, if an invalidation is required.
you should do this manually with this:
to ensure a clean update!
fixed in 1ae582b
fixes trac issue #4220