tests/test-backwards-remove.t

rebase: remove sortedstate-related confusion

The following rebase implementation details are frustrating:
- storing a list of sorted revision numbers in a field named sortedstate
- having sortedstate be a field of the rebaseruntime class
- using sortedstate[-1] as opposed to a more intuitive max(self.state) to
  compute the latest revision in the state

This commit fixes those imperfections.

  $ hg init
  $ echo This is file a1 > a
  $ hg add a
  $ hg commit -m "commit #0"
  $ ls
  a
  $ echo This is file b1 > b
  $ hg add b
  $ hg commit -m "commit #1"
  $ hg co 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

B should disappear

  $ ls
  a