tests/test-dirstate-backup.t

import-checker: make stdlib path detection work in virtual environments

The previous logic tried to find the directory containing BaseHTTPServer, which
didn’t work as indended because it was only present on Python 2. Instead, the
argparse module is used now.

Set up

  $ hg init repo
  $ cd repo
  $ echo a > a
  $ hg add a
  $ hg commit -m a

Try to import an empty patch

  $ hg import --no-commit - <<EOF
  > EOF
  applying patch from stdin
  abort: stdin: no diffs found
  [10]

No dirstate backups are left behind

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