Store path attribute on Diff object

If a file in a commit contains no changes (for example, if only the file mode is changed) there will be no blob attached. This is usually where the filename is stored, so without it, the calling context can not tell what file was changed. Instead, always store a_path and b_path on the Diff object so that information is available.

Author: jeblair

git/diff.py

@@ -168,11 +168,13 @@ class Diff(object):
 
  a_mode is None
  a_blob is None
+ a_path is None
 
  ``Deleted File``::
 
  b_mode is None
  b_blob is None
+ b_path is None
 
  ``Working Tree Blobs``
 
@@ -200,8 +202,8 @@ class Diff(object):
 NULL_HEX_SHA="0"*40
 NULL_BIN_SHA=b"\0"*20
 
-__slots__= ("a_blob", "b_blob", "a_mode", "b_mode", "new_file", "deleted_file",
-"rename_from", "rename_to", "diff")
+__slots__= ("a_blob", "b_blob", "a_mode", "b_mode", "a_path", "b_path",
+"new_file", "deleted_file", "rename_from", "rename_to", "diff")
 
 def__init__(self, repo, a_path, b_path, a_blob_id, b_blob_id, a_mode,
 b_mode, new_file, deleted_file, rename_from,
@@ -210,6 +212,9 @@ def __init__(self, repo, a_path, b_path, a_blob_id, b_blob_id, a_mode,
 self.a_mode=a_mode
 self.b_mode=b_mode
 
+self.a_path=a_path
+self.b_path=b_path
+
 ifself.a_mode:
 self.a_mode=mode_str_to_int(self.a_mode)
 ifself.b_mode: