[PATCH 1 of 4] revlog: remove unused variable 'chainlen'

[Martin von Zweigbergk]

# HG changeset patch
# User Martin von Zweigbergk <martinvonz at google.com>
# Date 1449278546 28800
#      Fri Dec 04 17:22:26 2015 -0800
# Node ID 7ab358606c379dffd78218a068a66cd2017a3ba5
# Parent  30a20167ae29e1874163b59a489de0cb1d859565
revlog: remove unused variable 'chainlen'

diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -1406,7 +1406,6 @@
         curr = len(self)
         prev = curr - 1
         base = chainbase = curr
-        chainlen = None
         offset = self.end(prev)
         delta = None
         if self._basecache is None: