diff -r 2c0570a6d5ae -r 5ad37b5bfb31 mercurial/commands.py
--- a/mercurial/commands.py	Mon May 02 12:10:28 2022 +0400
+++ b/mercurial/commands.py	Wed May 04 13:39:49 2022 -0400
@@ -2536,7 +2536,8 @@
 
        :hg:`diff` may generate unexpected results for merges, as it will
        default to comparing against the working directory's first
-       parent changeset if no revisions are specified.
+       parent changeset if no revisions are specified.  To diff against the
+       conflict regions, you can use `--config diff.merge=yes`.
 
     By default, the working directory files are compared to its first parent. To
     see the differences from another revision, use --from. To see the difference