tests/test-nested-repo.t

progress: split up _print() method in bar-updating and debug-printing

I just thought this was clearer, but it turned out to also simplify
the next patch.

This seems to have sped up `hg perfprogress` from 1.85 s to 1.78 s.

Differential Revision: https://phab.mercurial-scm.org/D5529

  $ hg init a
  $ cd a
  $ hg init b
  $ echo x > b/x

Should print nothing:

  $ hg add b
  $ hg st

  $ echo y > b/y
  $ hg st

Should fail:

  $ hg st b/x
  abort: path 'b/x' is inside nested repo 'b'
  [255]
  $ hg add b/x
  abort: path 'b/x' is inside nested repo 'b'
  [255]

Should fail:

  $ hg add b b/x
  abort: path 'b/x' is inside nested repo 'b'
  [255]
  $ hg st

Should arguably print nothing:

  $ hg st b

  $ echo a > a
  $ hg ci -Ama a

Should fail:

  $ hg mv a b
  abort: path 'b/a' is inside nested repo 'b'
  [255]
  $ hg st

  $ cd ..