fix(diff): use explicit change-type if possible

That way, we do not have to figure the change type out by examining the diff object. It's implemented in a way that should yield more desireable results as we keep the change-type that git is providing us with. Fixes#493

Author: Byron

doc/source/changes.rst

@@ -2,6 +2,12 @@
 Changelog
 =========
 
+2.0.8 - Bugfixes
+================
+
+* `DiffIndex.iter_change_type(...)` produces better results when diffing
+ an index against the working tree.
+
 2.0.7 - New Features
 ====================
 

git/diff.py

@@ -183,7 +183,9 @@ def iter_change_type(self, change_type):
 raiseValueError("Invalid change type: %s"%change_type)
 
 fordiffinself:
-ifchange_type=="A"anddiff.new_file:
+ifdiff.change_type==change_type:
+yielddiff
+elifchange_type=="A"anddiff.new_file:
 yielddiff
 elifchange_type=="D"anddiff.deleted_file:
 yielddiff
@@ -247,11 +249,12 @@ class Diff(object):
 NULL_BIN_SHA=b"\0"*20
 
 __slots__= ("a_blob", "b_blob", "a_mode", "b_mode", "a_rawpath", "b_rawpath",
-"new_file", "deleted_file", "raw_rename_from", "raw_rename_to", "diff")
+"new_file", "deleted_file", "raw_rename_from", "raw_rename_to",
+"diff", "change_type")
 
 def__init__(self, repo, a_rawpath, b_rawpath, a_blob_id, b_blob_id, a_mode,
 b_mode, new_file, deleted_file, raw_rename_from,
-raw_rename_to, diff):
+raw_rename_to, diff, change_type):
 
 self.a_mode=a_mode
 self.b_mode=b_mode
@@ -286,6 +289,7 @@ def __init__(self, repo, a_rawpath, b_rawpath, a_blob_id, b_blob_id, a_mode,
 self.raw_rename_to=raw_rename_toorNone
 
 self.diff=diff
+self.change_type=change_type
 
 def__eq__(self, other):
 fornameinself.__slots__:
@@ -435,7 +439,7 @@ def _index_from_patch_format(cls, repo, stream):
 new_file, deleted_file,
 rename_from,
 rename_to,
-None))
+None, None))
 
 previous_header=header
 # end for each header we parse
@@ -483,7 +487,7 @@ def _index_from_raw_format(cls, repo, stream):
 # END add/remove handling
 
 diff=Diff(repo, a_path, b_path, a_blob_id, b_blob_id, old_mode, new_mode,
-new_file, deleted_file, rename_from, rename_to, '')
+new_file, deleted_file, rename_from, rename_to, '', change_type)
 index.append(diff)
 # END for each line
 

git/test/fixtures/diff_abbrev-40_full-index_M_raw_no-color

@@ -0,0 +1 @@
+:100644 100644 739bc65220ad90e9ebfa2d6af1723b97555569a4 0000000000000000000000000000000000000000 M README.md

git/test/test_diff.py

@@ -104,6 +104,15 @@ def test_diff_with_rename(self):
 assertdiff.rename_to=='that'
 assertlen(list(diffs.iter_change_type('R'))) ==1
 
+deftest_diff_of_modified_files_not_added_to_the_index(self):
+output=StringProcessAdapter(fixture('diff_abbrev-40_full-index_M_raw_no-color'))
+diffs=Diff._index_from_raw_format(self.rorepo, output.stdout)
+
+assertlen(diffs) ==1, 'one modification'
+assertlen(list(diffs.iter_change_type('M'))) ==1, 'one modification'
+assertdiffs[0].change_type=='M'
+assertdiffs[0].b_blobisNone
+
 deftest_binary_diff(self):
 formethod, file_namein ((Diff._index_from_patch_format, 'diff_patch_binary'),
  (Diff._index_from_raw_format, 'diff_raw_binary')):