tests/test-empty.t

tests: allow the true command to be provided by coreutils

The `true` command is sometimes provided as a symbolic link to the `coreutils`
single binary. This is the case on NixOS, on which the test was failing because
the symbolic link fully resolves to the latter name, equally valid but not
previously accepted by the test's golden output.

Differential Revision: https://phab.mercurial-scm.org/D11740

Create an empty repo:

  $ hg init a
  $ cd a

Try some commands:

  $ hg log
  $ hg grep wah
  [1]
  $ hg manifest
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  checked 0 changesets with 0 changes to 0 files

Check the basic files created:

  $ ls .hg
  00changelog.i
  cache
  requires
  store
  wcache

Should be empty:

  $ ls .hg/store

Poke at a clone:

  $ cd ..
  $ hg clone a b
  updating to branch default
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd b
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  checked 0 changesets with 0 changes to 0 files
  $ ls .hg
  00changelog.i
  cache
  dirstate
  hgrc
  requires
  store
  wcache

Should be empty:

  $ ls .hg/store

  $ cd ..