[PATCH 0 of 2] phase mouvement with rebase and graft (update)

[alain.leufroy at logilab.fr]

I send these 2 patches again: there were coding style issues :/

Note that there is no change in the graft code as it actually does the trick. I've just added test
to validate the behaviour.

--

These 2 changesets fix phase mouvement with rebase and add test for graft.

Rebase:
  The idea is to _try_ to keep source phase on rebase.

Graft:
  The idea is not to keep the phase of the cherry-picked changesets
  because::

* draft is a copy if the "operations" made on the source changets while rebase is used to
  move changesets
* draft allow to reorder changesets


What do you think about the draft behaviour? It shall be same for transplant