tests/test-debugrename.t

changegroup: extract method that sorts nodes to send

The current implementation of narrowhg needs to influence the order in
which nodes are sent to the client. adgar@ and I think this is
fixable, but it's going to require pretty substantial time investment,
so in the interim we'd like to extract this method.

I think it makes the group() code a little more obvious, as it took us
a couple of tries to isolate the exact behavior we were observing.

  $ 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