[MERGE] Rename on Windows is able to change filename case. (#77740)

[Alexander Belchenko]

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Aaron Bentley пишет:
> Alexander Belchenko wrote:
>> Windows used case insensitive filesystem therefore rename (bzr mv) should care about special case
>> when only case is changed.
> 
> bb:comment
> 
> Could you please explain why we should avoid using fancy_rename in that
> special case.?

Because it simply did not work for this special case, but os.rename works just like a charm.

fancy_rename(old,new) try at first rename new (if exists) to some temp name, and therefore it move
away original file, because on case-insensitive filesystem 'test.txt' and 'Test.txt' is the same.
So fancy_rename actually mv *both* new and old to temp name. Then fancy_rename try to
`rename old new`, but at this point old is not exists, and here we get exception.
Then fancy_rename did rollback and restore new (that actually old) from temp file.

so on Windows:

os.rename('test.txt', 'Test.txt') => works
osutils.fancy_rename('test.txt', 'Test.txt') => fails with OSError (File not found).
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