diff kitten: Fix error when only RHS file is a binary file

Fixes #752

docs/changelog.rst

@@ -32,6 +32,10 @@ Changelog
   takes parameters so you can define your own shortcuts to clear the
   screen/scrollback also (:iss:`747`)
 
+- diff kitten: Fix error when right hand side file is binary and left hand side
+  file is text (:iss:`752`)
+
+
 0.11.3 [2018-07-10]
 ------------------------------
 

kittens/diff/main.py

@@ -42,7 +42,7 @@ def generate_diff(collection, context):
 
     for path, item_type, changed_path in collection:
         if item_type == 'diff':
-            is_binary = isinstance(data_for_path(path), bytes)
+            is_binary = isinstance(data_for_path(path), bytes) or isinstance(data_for_path(changed_path), bytes)
             if not is_binary:
                 d.add_diff(path, changed_path)
 

kittens/diff/render.py

@@ -452,8 +452,8 @@ def render_diff(collection, diff_map, args, columns, image_manager):
 
     for i, (path, item_type, other_path) in enumerate(collection):
         item_ref = Reference(path)
-        is_binary = isinstance(data_for_path(path), bytes)
+        is_binary = isinstance(data_for_path(path), bytes) or (other_path and isinstance(data_for_path(other_path), bytes))
-        is_img = is_binary and is_image(path) and images_supported()
+        is_img = is_binary and (is_image(path) or is_image(other_path)) and images_supported()
         yield from yield_lines_from(title_lines(path, other_path, args, columns, margin_size), item_ref, False)
         if item_type == 'diff':
             if is_binary: