add test to detect the corrupt log

- add a second line to commit messages with the "BAD MESSAGE" text
- read in the log and confirm that the seond line is not in the log file

git/test/test_repo.py

@@ -775,12 +775,23 @@ def test_empty_repo(self, rw_dir):
         new_file_path = os.path.join(rw_dir, "new_file.ext")
         touch(new_file_path)
         r.index.add([new_file_path])
-        r.index.commit("initial commit")
+        r.index.commit("initial commit\nBAD MESSAGE 1\n")
 
         # Now a branch should be creatable
         nb = r.create_head('foo')
         assert nb.is_valid()
 
+        with open( new_file_path, 'w' ) as f:
+            f.write( 'Line 1\n' )
+
+        r.index.add([new_file_path])
+        r.index.commit("add line 1\nBAD MESSAGE 2\n")
+
+        with open( '%s/.git/logs/refs/heads/master' % (rw_dir,), 'r' ) as f:
+            contents = f.read()
+
+        assert 'BAD MESSAGE' not in contents, 'log is corrupt'
+
     def test_merge_base(self):
         repo = self.rorepo
         c1 = 'f6aa8d1'