[Distutils] extending setuptools to use other revision control tools for --tag-svn-revision ?

[zooko]

Folks:

The allmydata.org tahoe project uses setuptools and the darcs  
revision control tool [1].

We've long since written a custom script to generate the version  
number from the revision control history.  With this we can update  
our release version number in exactly one place -- the revision  
control tool -- and the script produces the Python module's  
__version__ attribute as well as the setup.py's "version" argument.   
The script also produces the equivalent of "revision numbers" (which  
in darcs is the count of patches that have been applied since the  
last release tag).

You can see the details here: [2, 3, 4, 5].

The question is: is there a way to extend setuptools to do something  
like this for revision control tools other than svn?

Thank you for your time.

Regards,

Zooko

[1] http://darcs.net
[2] http://allmydata.org/trac/tahoe/browser/misc/make-version.py
[3] http://allmydata.org/trac/tahoe/browser/src/allmydata/__init__.py
[4] http://allmydata.org/trac/tahoe/browser/setup.py
[5] http://allmydata.org/trac/tahoe/browser/Makefile