tests/test-revert-flags.t

perf: add a `perfbranchmapupdate` command

This command benchmark the time necessary to update the branchmap between two
sets of revisions. This changeset introduce a first version, doing nothing fancy
regarding cache or other internal details.

#require execbit

  $ hg init repo
  $ cd repo
  $ echo foo > foo
  $ chmod 644 foo
  $ hg ci -qAm '644'

  $ chmod 755 foo
  $ hg ci -qAm '755'

reverting to rev 0

  $ hg revert -a -r 0
  reverting foo
  $ hg st
  M foo
  $ hg diff --git
  diff --git a/foo b/foo
  old mode 100755
  new mode 100644

  $ cd ..