diff --git a/mercurial/configitems.py b/mercurial/configitems.py
--- a/mercurial/configitems.py
+++ b/mercurial/configitems.py
@@ -774,7 +774,6 @@
     b'diff',
     b'merge',
     default=False,
-    experimental=True,
 )
 coreconfigitem(
     b'email',
diff --git a/mercurial/ui.py b/mercurial/ui.py
--- a/mercurial/ui.py
+++ b/mercurial/ui.py
@@ -81,6 +81,8 @@
 git = 1
 showfunc = 1
 word-diff = 1
+# use merge-diff functionality to make `diff` of a merge easier to understand
+merge = yes
 """
 
 samplehgrcs = {