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

[Alexander Belchenko]

Ian Clatworthy пишет:
> 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 

bb:abstain because this patch solve problem only at CLI level, but I think it's better to solve it 
at WorkingTree API level. Without solving it at WT API level each GUI application will duplicate 
this logic inside their own codebase.