Libification update

[Matthias Urlichs <smurf@smurf.noris.de>]

I've merged my current library-ification effort with Junio's current HEAD.

URL: http://netz.smurf.noris.de/git/git.git#libize

There's a Python interface, written using Pyrex. You can now walk object
trees natively, with Python:

>>> import git
>>> e=git.env()
>>> db=e.objdb
>>> c=db.lookup("HEAD").parent[0] # "HEAD^" will work too
>>> t=c.tree
>>> t.entries[0].name
'.gitignore'
>>> t["debian"].entries[0].name
'changelog'
>>> t[".gitignore"].data[0:5]
'/git\n'
>>> t[".gitignore"].data.readline()
'/git\n'    # this will work tomorrow (I hope)

I have not implemented much beyond that; keeping the code in sync is
work, so doing more will have to wait until this gets merged.

I did play with SWIG a bit. It would have simplified interfacing
languages other than Python to git. Unfortunately, there were problems: 

- refering to objects SWIG did not allocate itself is a nontrivial
  exercise
- so is keeping the Python-visible namespace clean
  (unless you're using C++ ... probably not something we'd want to subject
  the git core to ...)
- SWIG's error reporting is *scary*.
  In comparison, Pyrex mostly does the right thing.

If somebody wants to start working on a SWIG/perl/tcl/... interface
for the library, be my guest. ;-)

-- 
Matthias Urlichs   |   {M:U} IT Design @ m-u-it.de   |  smurf@smurf.noris.de
Disclaimer: The quote was selected randomly. Really. | http://smurf.noris.de
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