change decode type and add replace flag

Author: ishepard

git/diff.py

@@ -275,7 +275,7 @@ def __init__(self, repo, a_rawpath, b_rawpath, a_blob_id, b_blob_id, a_mode,
         # we need to overwrite "repo" to the corresponding submodule's repo instead
         if repo and a_rawpath:
             for submodule in repo.submodules:
-                if submodule.path == a_rawpath.decode("utf-8"):
+                if submodule.path == a_rawpath.decode(defenc, 'replace'):
                     if submodule.module_exists():
                         repo = submodule.module()
                     break