upgrade: explicitly test for revlog index

We do not want to exclude `.d` we want to only include `.i`. We are about to add
more extension type (for the persistent nodemap: `.n`, `.nd`) so lets make the
list explicit instead.

Differential Revision: https://phab.mercurial-scm.org/D9748

mercurial/upgrade_utils/engine.py

@@ -190,7 +190,7 b' def _clonerevlogs('
     # Perform a pass to collect metadata. This validates we can open all
     # source files and allows a unified progress bar to be displayed.
     for unencoded, encoded, size in alldatafiles:
-        if unencoded.endswith(b'.d'):
+        if not unencoded.endswith(b'.i'):
             continue
 
         rl = _revlogfrompath(srcrepo, unencoded)