copies: add a config to limit the number of candidates to check in heuristics The heuristics algorithm find possible candidates for move/copy and then check whether they are actually a copy or move. In some cases, there can be lot of candidates possible which can actually slow down the algorithm. This patch introduces a config option `experimental.copytrace.movecandidateslimit` using which one can limit the candidates to check. The limit defaults to 100. Thanks to Yuya for suggesting to skip copytracing for that file with a warning. Differential Revision: https://phab.mercurial-scm.org/D987

--- a/mercurial/configitems.py	Tue Oct 17 10:31:44 2017 -0700
+++ b/mercurial/configitems.py	Tue Oct 10 02:25:03 2017 +0530
@@ -330,6 +330,9 @@
 coreconfigitem('experimental', 'copytrace',
     default='on',
 )
+coreconfigitem('experimental', 'copytrace.movecandidateslimit',
+    default=100,
+)
 coreconfigitem('experimental', 'copytrace.sourcecommitlimit',
     default=100,
 )