tests/test-backwards-remove.t

repair: add experimental option to write bundle2 files

This adds an experimental option 'strip-bundle2-version' which causes backup
bundles to use bundle2 formatting.  Especially for generaldelta repositories,
this should provide significant performance gains for any operation that needs
to write a backup.

  $ 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