# HG changeset patch
# User Nathan Goldbaum <nathan12343@gmail.com>
# Date 2019-05-23 14:47:10
# Node ID a84564b1a0b1dd58174ff29adbf88a0a033e5251
# Parent  4372d56112c9b3b027b703cf261bc7cf858c1666

help: check if a subtopic exists and raise an error if it doesn't (issue6145)

Differential Revision: https://phab.mercurial-scm.org/D6441

diff --git a/mercurial/help.py b/mercurial/help.py
--- a/mercurial/help.py
+++ b/mercurial/help.py
@@ -689,6 +689,8 @@ def help_(ui, commands, name, unknowncmd
             for names, header, doc in subtopics[name]:
                 if subtopic in names:
                     break
+            if not any(subtopic in s[0] for s in subtopics[name]):
+                raise error.UnknownCommand(name)
 
         if not header:
             for topic in helptable: