tests/test-dirstate-backup.t

wireproto: port protocol handler to zope.interface

zope.interface is superior to the abc module. Let's port to it.

As part of this, we add tests for interface conformance for
classes implementing the interface.

Differential Revision: https://phab.mercurial-scm.org/D2983

Set up

  $ hg init repo
  $ cd repo

Try to import an empty patch

  $ hg import --no-commit - <<EOF
  > EOF
  applying patch from stdin
  abort: stdin: no diffs found
  [255]

No dirstate backups are left behind

  $ ls .hg/dirstate* | sort
  .hg/dirstate