[MERGE] Initialize before transfer for BzrDir.clone() and sprout()

[Robert Collins]

Robert Collins has voted +0.
Status is now: Semi-approved
Comment:
I think the basic tension is whether branch/push operations should be 
resumable on error or not.

If they should be then creating a blank branch is clearly the right 
thing. If they shouldn't, then I dont think a branch should be created 
at all until the repository is populated - push can just create the 
branch later. [and branch creation can be done via a tempdir + rename 
approach when the branch object is actually created].

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C458B19D2.3090704%40arbash-meinel.com%3E