diff --git a/mercurial/commands.py b/mercurial/commands.py
--- a/mercurial/commands.py
+++ b/mercurial/commands.py
@@ -3318,7 +3318,7 @@
     ]
     + formatteropts
     + walkopts,
-    _(b'[OPTION]... PATTERN [FILE]...'),
+    _(b'[--diff] [OPTION]... PATTERN [FILE]...'),
     helpcategory=command.CATEGORY_FILE_CONTENTS,
     inferrepo=True,
     intents={INTENT_READONLY},