tests/test-empty-dir.t

localrepo: reverse contexts in status

This is a slight tweak to how localrepo.status calculates what files have
changed. By forcing a changectx to be first operator and anything not a
changectx to be the second operator, we can later exploit this to allow
refactoring the status operation as a method of a context object.

Furthermore, this change will speed up 'hg diff --reverse' when used with the
working directory because the code will now hit a fast path without needing to
calculate an unneeded second manifest.

  $ 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