tests/test-issue1089.t

pathutil: use `finddirs_rev_noroot` instead of `parts`

The benefit this brings is very tiny, if it's even there,
since we still didn't get rid of the [parts] computation.

It probably won't be worth it without the subsequent patch
that adds one more use of [finddirs_rev_noroot]

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

  $ hg init repo
  $ cd repo
  $ 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 ..