Support bytes(x) on git objects.

Disable __str__ on Python3, since there is no unicode string
representation of these objects.

Fixes #609

dulwich/objects.py

@@ -27,6 +27,7 @@ from collections import namedtuple
 import os
 import posixpath
 import stat
+import sys
 import warnings
 import zlib
 from hashlib import sha1
@@ -304,9 +305,14 @@ class ShaFile(object):
         """
         return b''.join(self.as_raw_chunks())
 
-    def __str__(self):
-        """Return raw string serialization of this object."""
-        return self.as_raw_string()
+    if sys.version_info[0] >= 3:
+        def __bytes__(self):
+            """Return raw string serialization of this object."""
+            return self.as_raw_string()
+    else:
+        def __str__(self):
+            """Return raw string serialization of this object."""
+            return self.as_raw_string()
 
     def __hash__(self):
         """Return unique hash for this object."""

dulwich/tests/test_objects.py

@@ -159,6 +159,7 @@ class BlobReadTests(TestCase):
         self.assertEqual(b'test 5\n', b.data)
         b.chunked = [b'te', b'st', b' 6\n']
         self.assertEqual(b'test 6\n', b.as_raw_string())
+        self.assertEqual(b'test 6\n', bytes(b))
 
     def test_parse_legacy_blob(self):
         string = b'test 3\n'
@@ -793,6 +794,8 @@ class TreeTests(ShaFileCheckTests):
         x[b'myname'] = (0o100755, myhexsha)
         self.assertEqual(b'100755 myname\0' + hex_to_sha(myhexsha),
                          x.as_raw_string())
+        self.assertEqual(b'100755 myname\0' + hex_to_sha(myhexsha),
+                         bytes(x))
 
     def test_tree_update_id(self):
         x = Tree()