localrepo: mark nullrev has never filtered

All repository have a null, and it cannot be filtered.

Differential Revision: https://phab.mercurial-scm.org/D7484

mercurial/localrepo.py

@@ -1532,7 +1532,7 b' class localrepository(object):'
 
         # dealing with some special values
         if changeid == b'null' or changeid == nullrev:
-            return context.changectx(self, nullrev, nullid)
+            return context.changectx(self, nullrev, nullid, maybe_filtered=False)
         if changeid == b'tip':
             node = self.changelog.tip()
             rev = self.changelog.rev(node)

tests/test-repo-filters-tiptoe.t

@@ -54,6 +54,5 b' Getting the node of `null`'
 Getting basic changeset inforation about `null`
 
   $ hg log -r null -T "{node}\n{date}\n"
-  debug.filters: computing revision filter for "visible"
   0000000000000000000000000000000000000000
   0.00