[MERGE][BUG #177809] bzr SOURCE DESTINATION tweaks

[Ian Clatworthy]

Ian Clatworthy has voted tweak.
Status is now: Semi-approved
Comment:
Apologies for taking way too long to review this.

I've explained in comments on the bug why I think this is actually ok, 
despite originally agreeing with Alexander's view. The only bit I don't 
like is that duplicate files are silently ignored by design, e.g.

   bzr mv a a b/

just works without a warning. It turns out that's consistent with add 
and delete, so fair enough. I would like the help (docstring) expanded 
though to mention this behaviour.

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C64ab70ac0802041811u61752e66l3a04f025336390ae%40mail.gmail.com%3E