[Distutils] setuptools 0.5a12

[Phillip J. Eby]

Hopefully, this is the last of the current spew of bugfix releases, 
although in this case I also threw in some revisions to pkg_resources' 
handling of resource extraction.  You can now control the cache explicitly 
using a PYTHON_EGGS_CACHE variable, and on Windows the default if you don't 
specify it is now a "Python-Eggs" directory under the current user's 
"application data" directory.  Also, extraction takes place to a temporary 
filename that is then renamed to the final name, in order to prevent race 
conditions with other threads or processes.  So, assuming this change works 
well, I will start making the zip safety checks a little less stringent, so 
that mere use of C extensions or data files won't disqualify an egg from 
being installed in zipped form.

However, that will be in the 0.6 series of releases, which will be focused 
mainly on getting both pkg_resources and the entire easy_install family of 
code under a solid test regime.  I'm currently releasing as many new bugs 
as I am new features, so that's got to stop right away.  My current plan is 
to see if I can jury-rig doctest to do tests on the output of various 
easy_install commands, running them in various temporary environments.  The 
result of this process may be that EasyInstall ends up with additional 
options to control testing behavior.  (For example, I can't test 
easy-install.pth manipulation by installing to a temporary directory!)

As part of the move to full test automation, I'll also be refactoring 
pkg_resources to match the design I posted here a while back, and 
implementing core engine features like Ryan's "legacy.py" option, my 
"add_activation_listener()", etc.  The PythonEggs page could really use 
some updating, too, to catch up even to the current API, let alone the 
future one.  It also has some bits that should be removed since they 
document manual ways to do things that setuptools does 
automatically.  (e.g. creating a 'depends.txt' file when setuptools now 
just uses the 'install_requires' and 'extras_require' keywords.