perf: make `perfnodemap` use the new `index.get_rev` api if available

Differential Revision: https://phab.mercurial-scm.org/D7358

contrib/perf.py

@@ -1629,7 +1629,11 b' def perfnodemap(ui, repo, **opts):'
     def setnodeget():
         # probably not necessary, but for good measure
         clearchangelog(unfi)
-        nodeget[0] = makecl(unfi).nodemap.get
+        cl = makecl(unfi)
+        if util.safehasattr(cl.index, 'get_rev'):
+            nodeget[0] = cl.index.get_rev
+        else:
+            nodeget[0] = cl.nodemap.get
 
     def d():
         get = nodeget[0]