tests/test-dirstate-backup.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.

Set up

  $ hg init repo
  $ cd repo

Try to import an empty patch

  $ hg import --no-commit - <<EOF
  > EOF
  applying patch from stdin
  abort: stdin: no diffs found
  [255]

No dirstate backups are left behind

  $ ls .hg/dirstate* | sort
  .hg/dirstate