This allows additional commands to be provided for
existing setup.py scripts without modifying either the
distutils installation or the setup.py scripts of
packages with which the new commands will be used.

Specifically, an option is added to distutils that
allows additional packages to be searched for command
implementations in addition to distutils.command.  The
additional packages can be specified on the command
line or via the installation or personal configuration
files already loaded by distutils.

For discussion, see the thread starting with:

http://mail.python.org/pipermail/distutils-sig/2004-August/004112.html

This patch adds the feature and unit tests; I'll add an
additional patch with documentation updates when that's
ready.

I'd like this to appear in the 2.4a2 release.

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I've replaced the implementation patch with one that has
unit tests that are not sensitive to existing distutils
config files.

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Committed as:

Doc/dist/dist.tex  1.81
Lib/distutils/dist.py  1.68
Lib/distutils/tests/test_dist.py  1.1