tests/test-debugrename.t

ui: add new config option for help text width

Before this patch, when printing help text using `hg help`, or `hg log -h`,
the output will wrap at 78 chars even if the user has a bigger terminal width
and there is no config option to change it, making the experience different
from the commonly used `man` tool.

This patch introduces a new config option `ui.textwidth`, which replaces the
hardcoded number. It's set to 78 by default to maintain compatibility. When
set to 0, `hg help` will behave more like `man`.

  $ 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