tests/test-backwards-remove.t

dirstate-item: change the internal storage and constructor value

This should be closer to what we do need and what we can actually reliably
record.

In practice it means that we abandon the prospect of storing much more refined
data for now. We don't have the necessary information nor code using it right
now. So it seems safer to just use a clearer version of what we had so far.

See the documentation changes for details.

Differential Revision: https://phab.mercurial-scm.org/D11557

  $ hg init
  $ echo This is file a1 > a
  $ hg add a
  $ hg commit -m "commit #0"
  $ ls -A
  .hg
  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
  .hg
  a