manifest: use rev() instead of nodemap.__contains__

nodemap is an implementation detail of revlogs and isn't
appropriate to expose on the manifest storage API.

While revlogs don't have a __contains__, they do have lookup()
for resolving a value to a node. And this calls rev(), whose API
is documented to raise LookupError if a node doesn't exist. And
the parameters to LookupError are identical to what was being
raised here. So this change should be backwards compatible.

Differential Revision: https://phab.mercurial-scm.org/D4279

mercurial/manifest.py

@@ -1453,10 +1453,10 b' class manifestlog(object):'
         if tree:
             if self._revlog._treeondisk:
                 if verify:
-                    dirlog = self.getstorage(tree)
-                    if node not in dirlog.nodemap:
-                        raise LookupError(node, dirlog.indexfile,
-                                          _('no node'))
+                    # Side-effect is LookupError is raised if node doesn't
+                    # exist.
+                    self.getstorage(tree).rev(node)
+
                 m = treemanifestctx(self, tree, node)
             else:
                 raise error.Abort(
@@ -1464,9 +1464,9 b' class manifestlog(object):'
                           "manifest") % tree)
         else:
             if verify:
-                if node not in self._revlog.nodemap:
-                    raise LookupError(node, self._revlog.indexfile,
-                                      _('no node'))
+                # Side-effect is LookupError is raised if node doesn't exist.
+                self._revlog.rev(node)
+
             if self._treemanifests:
                 m = treemanifestctx(self, '', node)
             else: