diff -r 5e4027db52f4 -r bfcd5c7cbf9a mercurial/configitems.py
--- a/mercurial/configitems.py	Wed Jul 11 21:51:47 2018 +0900
+++ b/mercurial/configitems.py	Wed Jul 11 22:06:04 2018 +0900
@@ -188,7 +188,7 @@
     default=dynamicdefault,
 )
 coreconfigitem('commands', 'grep.all-files',
-    default=True,
+    default=False,
 )
 coreconfigitem('commands', 'show.aliasprefix',
     default=list,