mercurial/scmutil.py

--- a/mercurial/scmutil.py	Sun Jul 29 16:25:51 2018 +0900
+++ b/mercurial/scmutil.py	Mon Jul 30 15:53:47 2018 +0200
@@ -1366,7 +1366,8 @@
     """
     # experimental config: format.generaldelta
     return (ui.configbool('format', 'generaldelta')
-            or ui.configbool('format', 'usegeneraldelta'))
+            or ui.configbool('format', 'usegeneraldelta')
+            or ui.configbool('format', 'sparse-revlog'))
 
 def gddeltaconfig(ui):
     """helper function to know if incoming delta should be optimised