[PATCH 3 of 3] perfchangelog: add 'perfchangelog' command

[Pierre-Yves David]

# HG changeset patch
# User Pierre-Yves David <pierre-yves.david at octobus.net>
# Date 1495499078 -7200
#      Tue May 23 02:24:38 2017 +0200
# Node ID 73e20c262b133cf3117a7148e6293b5721e8930d
# Parent  c79b8f2a95a35ce1b41325d003337c65bc5bffca
# EXP-Topic perf
# Available At https://www.mercurial-scm.org/repo/users/marmoute/mercurial/
#              hg pull https://www.mercurial-scm.org/repo/users/marmoute/mercurial/ -r 73e20c262b13
perfchangelog: add 'perfchangelog' command

That command monitor the time spend initializing a new changelog object.
If I'm not mistaken this includes reading the file on disk and building the
nodemap.

diff --git a/contrib/perf.py b/contrib/perf.py
--- a/contrib/perf.py
+++ b/contrib/perf.py
@@ -488,6 +488,22 @@ def perfchangegroupchangelog(ui, repo, v
     timer(d)
     fm.end()
 
+def _clearchangelog(repo):
+    if 'changelog' in vars(repo):
+        del repo.changelog
+        del repo._filecache['changelog']
+
+ at command('perfchangelog', [], "")
+def perfchangelog(ui, repo, **opts):
+    """benchmark the changelog initialization"""
+    timer, fm = gettimer(ui, opts)
+    repo = repo.unfiltered()
+    def d():
+        _clearchangelog(repo)
+        repo.changelog
+    timer(d)
+    fm.end()
+
 @command('perfdirs', formatteropts)
 def perfdirs(ui, repo, **opts):
     timer, fm = gettimer(ui, opts)
diff --git a/tests/test-contrib-perf.t b/tests/test-contrib-perf.t
--- a/tests/test-contrib-perf.t
+++ b/tests/test-contrib-perf.t
@@ -56,6 +56,8 @@ perfstatus
    perfcca       (no help text available)
    perfchangegroupchangelog
                  Benchmark producing a changelog group for a changegroup.
+   perfchangelog
+                 benchmark the changelog initialization
    perfchangeset
                  (no help text available)
    perfctxfiles  (no help text available)