Re: [PATCH v12 5/5] read-cache: speed up has_dir_name (part 2)

>> +				 * last: xxx/yy-file (because '-' sorts before '/')
>> +				 * this: xxx/yy/abc
>
> This is problematic, because the index can already contain 'xxx/yy' as
> a file, when adding 'xxx/yy/abc', but since 'xxx/yy' as a file sorts
> before 'xxx/yy-file', the short-circuiting here doesn't see it and
> thus leaves the d-f collision undetected.  Consequently, even Git
> porcelain commands can create tree objects with duplicate entries, as
> demonstrated in the tests below.