tests/test-debugrename.t

color: respect HGPLAINEXCEPT=color to allow colors while scripting (issue5749)

I'd also like --color=always on the command-line to override HGPLAIN=1
et al, but that's more work, and this seems like a better fix. We've
got a fair number of programs that actually want to automate hg and
get colored output to users, so they should set HGPLAINEXCEPT=alias
(what we usually recommend), but this has been breaking them because
they then lose color.

.. feature::

  The ``HGPLAINEXCEPT`` environment variable can now include ``color``
  to allow automatic output colorization in otherwise automated
  environments.

Differential Revision: https://phab.mercurial-scm.org/D1532

  $ hg init
  $ echo a > a
  $ hg ci -Am t
  adding a

  $ hg mv a b
  $ hg ci -Am t1
  $ hg debugrename b
  b renamed from a:b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3

  $ hg mv b a
  $ hg ci -Am t2
  $ hg debugrename a
  a renamed from b:37d9b5d994eab34eda9c16b195ace52c7b129980

  $ hg debugrename --rev 1 b
  b renamed from a:b789fdd96dc2f3bd229c1dd8eedf0fc60e2b68e3