[MERGE] Make 'mv a b' work for already renamed directories, like it does for files

[Alexander Belchenko]

Alexander Belchenko has voted comment.
Status is now: Waiting
Comment:
Your patch lacks support for case-insensitive filesystem. In the case of 
renaming directory and change only case `bzr mv` reports about error:

C:\work> python bzr st
removed:
   man1/
unknown:
   Man1/

C:\work> python bzr mv man1 Man1
bzr: ERROR: Could not move to Man1: Man1 is not versioned.

even with --after option.

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C1201432703.7423.3.camel%40nemo%3E