configitems: register 'ui.interactive'

That item default value is a bit special (None) so this adds a second proof
that everything is still working fine.

mercurial/configitems.py

@@ -42,6 +42,9 b" coreconfigitem('patch', 'fuzz',"
 coreconfigitem('ui', 'clonebundleprefers',
     default=[],
 )
+coreconfigitem('ui', 'interactive',
+    default=None,
+)
 coreconfigitem('ui', 'quiet',
     default=False,
 )

mercurial/ui.py

@@ -1139,7 +1139,7 b' class ui(object):'
 
         This function refers to input only; for output, see `ui.formatted()'.
         '''
-        i = self.configbool("ui", "interactive", None)
+        i = self.configbool("ui", "interactive")
         if i is None:
             # some environments replace stdin without implementing isatty
             # usually those are non-interactive

tests/test-devel-warnings.t

@@ -211,5 +211,6 b' Test warning on config option access and'
 
   $ hg --config "extensions.buggyconfig=${TESTTMP}/buggyconfig.py" buggyconfig
   devel-warn: specifying a default value for a registered config item: 'ui.quiet' 'False' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
+  devel-warn: specifying a default value for a registered config item: 'ui.interactive' 'None' at: $TESTTMP/buggyconfig.py:* (cmdbuggyconfig) (glob)
 
   $ cd ..