tests/test-issue1089.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.

https://bz.mercurial-scm.org/1089

  $ hg init
  $ mkdir a
  $ echo a > a/b
  $ hg ci -Am m
  adding a/b

  $ hg rm a
  removing a/b
  $ hg ci -m m a

  $ mkdir a b
  $ echo a > a/b
  $ hg ci -Am m
  adding a/b

  $ hg rm a
  removing a/b
  $ cd b

Relative delete:

  $ hg ci -m m ../a

  $ cd ..