tests/test-issue1089.t

rebase: remove redundant isinmemory argument from _origrebase()

The argument is redundant with `rbst.inmemory`, which makes it unclear
what to do if they were somehow different.

Differential Revision: https://phab.mercurial-scm.org/D9070

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 ..