diff -r bbf7a29dcf9b -r 6c80f985a13c mercurial/mdiff.py
--- a/mercurial/mdiff.py	Wed Mar 29 20:19:26 2017 -0700
+++ b/mercurial/mdiff.py	Sun Mar 26 20:52:51 2017 +0530
@@ -229,7 +229,7 @@
 
     def checknonewline(lines):
         for text in lines:
-            if text[-1] != '\n':
+            if text[-1:] != '\n':
                 text += "\n\ No newline at end of file\n"
             yield text