nodemap: use data from the index in debugnodemap --dump-new

It is better to run the actual code when generating a new nodemap cache from
scratch. So we do.

Differential Revision: https://phab.mercurial-scm.org/D8163

mercurial/debugcommands.py

@@ -2109,6 +2109,9 b' def debugnodemap(ui, repo, **opts):'
     if opts['dump_new']:
         unfi = repo.unfiltered()
         cl = unfi.changelog
+        if util.safehasattr(cl.index, "nodemap_data_all"):
+            data = cl.index.nodemap_data_all()
+        else:
         data = nodemap.persistent_data(cl.index)
         ui.write(data)
     elif opts['dump_disk']: