help: don't crash on help for 'sections' with multiple '.'

mercurial/commands.py

@@ -3837,7 +3837,7 b' def help_(ui, name=None, **opts):'
 
     section = None
     if name and '.' in name:
-        name, section = name.split('.')
+        name, section = name.split('.', 1)
 
     text = help.help_(ui, name, **opts)
 

tests/test-help.t

@@ -1094,6 +1094,10 b' Test section lookup'
   abort: help section not found
   [255]
 
+  $ hg help glossary.mc.guffin
+  abort: help section not found
+  [255]
+
 Test usage of section marks in help documents
 
   $ cd "$TESTDIR"/../doc