# HG changeset patch
# User Gregory Szorc <gregory.szorc@gmail.com>
# Date 1474745137 25200
# Node ID 5e72129d75edc2535f17d3b2a960d993bafc01a9
# Parent  edb49a90723cf54272c8dd57bbd76a092e16abe8
revlog: add instance variable controlling delta chain use

This is to support disabling delta chains on the changelog in a
subsequent patch.

diff -r edb49a90723c -r 5e72129d75ed mercurial/revlog.py
--- a/mercurial/revlog.py	Thu Oct 13 12:49:47 2016 +0200
+++ b/mercurial/revlog.py	Sat Sep 24 12:25:37 2016 -0700
@@ -297,6 +297,8 @@
             raise RevlogError(_("index %s unknown format %d")
                               % (self.indexfile, fmt))
 
+        self._storedeltachains = True
+
         self._io = revlogio()
         if self.version == REVLOGV0:
             self._io = revlogoldio()
@@ -1469,7 +1471,7 @@
             textlen = len(text)
 
         # should we try to build a delta?
-        if prev != nullrev:
+        if prev != nullrev and self._storedeltachains:
             tested = set()
             # This condition is true most of the time when processing
             # changegroup data into a generaldelta repo. The only time it