tests/test-empty-dir.t

rust-dirstate: call rust dirstatemap from Python

Since Rust-backed Python classes cannot be used as baseclasses (for
rust-cpython anyway), we use composition rather than inheritance.

This also allows us to keep the IO operations in the Python side, removing
(for now) the need to rewrite VFS in Rust, which would be a heavy undertaking.

Differential Revision: https://phab.mercurial-scm.org/D6634

  $ hg init

  $ echo 123 > a
  $ hg add a
  $ hg commit -m "first" a

  $ mkdir sub
  $ echo 321 > sub/b
  $ hg add sub/b
  $ hg commit -m "second" sub/b

  $ cat sub/b
  321

  $ hg co 0
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ cat sub/b 2>/dev/null || echo "sub/b not present"
  sub/b not present

  $ test -d sub || echo "sub not present"
  sub not present