fix(blame): lazily fetch full commit message

That way, we will not only get the summary line
contained in the blame, but fetch the full message.
This is more costly than the previous implementation
allowed it to be, but being less surprising/correct
certainly is the preferred behaviour here.

Fixes #485

Author: Byron

Diff for: git/repo/base.py

@@ -714,8 +714,7 @@ def blame_incremental(self, rev, file, **kwargs):
                            authored_date=int(props[b'author-time']),
                            committer=Actor(safe_decode(props[b'committer']),
                                            safe_decode(props[b'committer-mail'].lstrip(b'<').rstrip(b'>'))),
-                           committed_date=int(props[b'committer-time']),
-                           message=safe_decode(props[b'summary']))
+                           committed_date=int(props[b'committer-time']))
                 commits[hexsha] = c
             else:
                 # Discard the next line (it's a filename end tag)
@@ -815,8 +814,7 @@ def blame(self, rev, file, incremental=False, **kwargs):
                                            authored_date=info['author_date'],
                                            committer=Actor._from_string(
                                                info['committer'] + ' ' + info['committer_email']),
-                                           committed_date=info['committer_date'],
-                                           message=info['summary'])
+                                           committed_date=info['committer_date'])
                                 commits[sha] = c
                             # END if commit objects needs initial creation
                             if not is_binary:

Diff for: git/test/test_repo.py

@@ -307,7 +307,7 @@ def test_should_display_blame_information(self, git):
         assert_equal('Tom Preston-Werner', c.committer.name)
         assert_equal('[email protected]', c.committer.email)
         assert_equal(1191997100, c.committed_date)
-        assert_equal('initial grit setup', c.message)
+        self.assertRaisesRegexp(ValueError, "634396b2f541a9f2d58b00be1a07f0c358b999b3 missing", lambda: c.message)
 
         # test the 'lines per commit' entries
         tlist = b[0][1]