GPG signature support on commit object.

[sugi]

Current version fails if any commit object has GPG signeture.

It works by just deleting lines from 433 to 440 of git/objects/commit.py.

I can't find documentation of git object format. But I tried to write support
GPG signature on commit object.

Please consider to merge.

Here is the way to reproduce problem:

sugi@vaj-k-334-sugi:~% mkdir signed-test
sugi@vaj-k-334-sugi:~% cd  signed-test
sugi@vaj-k-334-sugi:~/signed-tes/% git init
Initialized empty Git repository in /home/sugi/signed-test/.git/
git@vaj-k-334-sugi:~/signed-test% date > date.txt
sugi@vaj-k-334-sugi:~/signed-test% git add .
sugi@vaj-k-334-sugi:~/signed-test% git commit -S -m 'Test commit with GPG sig.'

You need a passphrase to unlock the secret key for
user: "Tatsuki Sugiura <sugi@nemui.org>"
1024-bit DSA key, ID 4502FDC2, created 2000-09-30

gpg: gpg-agent is not available in this session
[master (root-commit) afad9ad] Test commit with GPG sig.
 1 file changed, 1 insertion(+)
 create mode 100644 date.txt
sugi@vaj-k-334-sugi:~/signed-test% git cat-file commit HEAD
tree 9165a13698f6b211db3d9631958ef11e8d06d477
author Tatsuki Sugiura <sugi@nemui.org> 1336266773 +0900
committer Tatsuki Sugiura <sugi@nemui.org> 1336266773 +0900
gpgsig -----BEGIN PGP SIGNATURE-----
 Version: GnuPG v1.4.12 (GNU/Linux)

 iEYEABECAAYFAk+l0BUACgkQbK2FzkUC/cLR9wCeKUkjeA39+vy0T/TwJuqPhca3
 eNMAnRw0tDNAqIcM4HJnHvzCsu86dLGV
 =ZlAu
 -----END PGP SIGNATURE-----

Test commit with GPG sig.
sugi@vaj-k-334-sugi:~/signed-test% python    
Python 2.7.3rc2 (default, Apr 22 2012, 22:35:38) 
[GCC 4.6.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import git
>>> git = git.Repo("/home/sugi/signed-test")
>>> git.commit()
<git.Commit "afad9ad7986c98784288ae71deb696d505cdfe5c">
>>> git.commit().author
afad9ad7986c98784288ae71deb696d505cdfe5c
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/sugi/lib/python2.7/site-packages/gitdb-0.5.4-py2.7-linux-x86_64.egg/gitdb/util.py", line 238, in __getattr__
    self._set_cache_(attr)
  File "/home/sugi/lib/python2.7/site-packages/GitPython-0.3.2.RC1-py2.7.egg/git/objects/commit.py", line 133, in _set_cache_
    self._deserialize(StringIO(stream.read()))
  File "/home/sugi/lib/python2.7/site-packages/GitPython-0.3.2.RC1-py2.7.egg/git/objects/commit.py", line 444, in _deserialize
    self.author.name = self.author.name.decode(self.encoding) 
LookupError: unknown encoding: -----BEGIN PGP SIGNATURE-----

[Byron]

Hi Sugi,

Thanks for discovering and fixing the issue. It would be great if you could add a test to verify it truly works.

Thanks,
Sebastian

[sugi]

Thank you for your reply!

OK. I'd like to write test. But I need time.

[kisoku]

We've encountered the exact same issue where I work. Our fix is also identical, we're still in the process of testing the patch. +1 on this pull request.

[sugi]

I rewrite this patch and sent new pull request against current master as #124.
Please continue to review new one.