basectx: move substate from changectx

mercurial/context.py

@@ -53,6 +53,10 b' class basectx(object):'
     def __ne__(self, other):
         return not (self == other)
 
+    @propertycache
+    def substate(self):
+        return subrepo.state(self, self._repo.ui)
+
     def rev(self):
         return self._rev
     def node(self):
@@ -193,10 +197,6 b' class changectx(basectx):'
             p = p[:-1]
         return [changectx(self._repo, x) for x in p]
 
-    @propertycache
-    def substate(self):
-        return subrepo.state(self, self._repo.ui)
-
     def __contains__(self, key):
         return key in self._manifest