perf: fix perfrevlogrevisions --reverse Currently, 'endrev' equals `len(revlog)`, a revision that does not exist. When asking for the reverse order, the arguments passed to xrange are `xrange(len(revlog), startrev)` which then crash. We need to offset 'endrev' by one so we don't crash anymore. Also, we offset 'startrev' to ensure we get the same number of revisions with and without the `--reverse` option. Differential Revision: https://phab.mercurial-scm.org/D5228

--- a/contrib/perf.py	Tue Nov 06 11:54:15 2018 +0100
+++ b/contrib/perf.py	Mon Nov 05 17:24:39 2018 +0100
@@ -1553,7 +1553,7 @@
         dist = opts[b'dist']
 
         if reverse:
-            beginrev, endrev = endrev, beginrev
+            beginrev, endrev = endrev - 1, beginrev - 1
             dist = -1 * dist
 
         for x in _xrange(beginrev, endrev, dist):