nodemap: only use persistent nodemap for non-inlined revlog

Revlog are inlined while they are small (to avoid having too many file to deal
with). The persistent nodemap will only provides a significant boost for large
enough revlog index. So it does not make sens to add an extra file to store
nodemap for small revlog.

We could consider inclining the nodemap data inside the revlog itself, but the
benefit is unclear so let it be an adventure for another time.

Differential Revision: https://phab.mercurial-scm.org/D7837

mercurial/revlog.py

@@ -1965,6 +1965,7 b' class revlog(object):'
             # manager
 
         tr.replace(self.indexfile, trindex * self._io.size)
+        nodemaputil.setup_persistent_nodemap(tr, self)
         self._chunkclear()
 
     def _nodeduplicatecallback(self, transaction, node):

mercurial/revlogutils/nodemap.py

@@ -34,6 +34,8 b' def setup_persistent_nodemap(tr, revlog)'
 
     (only actually persist the nodemap if this is relevant for this revlog)
     """
+    if revlog._inline:
+        return  # inlined revlog are too small for this to be relevant
     if revlog.nodemap_file is None:
         return  # we do not use persistent_nodemap on this revlog
     callback_id = b"revlog-persistent-nodemap-%s" % revlog.nodemap_file