$ 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