help: normalize extension shadow hint

mercurial/help.py

@@ -276,8 +276,8 b' def help_(ui, name, unknowncmd=False, fu'
             mod = extensions.find(name)
             doc = gettext(mod.__doc__) or ''
             if '\n' in doc.strip():
-                msg = _('use "hg help -e %s" to show help for '
-                        'the %s extension') % (name, name)
+                msg = _('(use "hg help -e %s" to show help for '
+                        'the %s extension)') % (name, name)
                 rst.append('\n%s\n' % msg)
         except KeyError:
             pass

tests/test-extension.t

@@ -388,7 +388,7 b' Extension module help vs command help:'
       compared to the working directory, and, when no revisions are specified,
       the working directory files are compared to its parent.
   
-  use "hg help -e extdiff" to show help for the extdiff extension
+  (use "hg help -e extdiff" to show help for the extdiff extension)
   
   options:
   

tests/test-strip.t

@@ -532,7 +532,7 b' Make sure no one adds back a -b option:'
   
   strip changesets and all their descendants from the repository
   
-  use "hg help -e strip" to show help for the strip extension
+  (use "hg help -e strip" to show help for the strip extension)
   
   options: