templater: add class representing a nested mappings The mappinggenerator class is necessary to fix hgweb bugs without BC. The mappinglist is for nested formatter items. They are similar, so factored out the base class. The mappinglist could be implemented by using the mappinggenerator, but we'll probably need a direct access to the raw list, so they are implemented as separate classes. Note that tovalue() isn't conforming to the spec yet in that it may return a list of dicts containing unprintable resources. This problem will be fixed later. Tests will be added by subsequent patches.

--- a/mercurial/templater.py	Sat Mar 17 22:56:49 2018 +0900
+++ b/mercurial/templater.py	Sat Mar 17 22:47:02 2018 +0900
@@ -44,6 +44,10 @@
 
 mappable
     represents a scalar printable value, also supports % operator.
+
+mappinggenerator, mappinglist
+    represents mappings (i.e. a list of dicts), which may have default
+    output format.
 """
 
 from __future__ import absolute_import, print_function