mercurial/diffhelpers.py

--- a/mercurial/diffhelpers.py	Mon Apr 09 21:06:46 2018 +0900
+++ b/mercurial/diffhelpers.py	Mon Apr 09 21:08:52 2018 +0900
@@ -70,8 +70,8 @@
     alen = len(a)
     blen = len(b)
     if alen > blen - bstart:
-        return -1
+        return False
     for i in xrange(alen):
         if a[i][1:] != b[i + bstart]:
-            return -1
-    return 0
+            return False
+    return True