Allow multiple libraries with the same hash.

[taralx]

Removes the need for canonicalization to prevent #12459.

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[retep998]

If we just want to know whether two files with the same name are actually the same file, I know there is a way on Windows to just check the IDs of files to see if they're the same (and it works with hard links too). Either GetFileInformationByHandle which returns a 64-bit ID + 32-bit volume ID which is unique on everything except ReFS which is for newer Windows only where you'd have to call GetFileInformationByHandleEx to get a FILE_ID_INFO with a 128-bit ID + 64-bit volume ID. Unsure about other platforms though, but if they can do this too then there is no need to canonicalize or to allow duplicate files.

[taralx]

There's no need to know if two files are the same file. If they have the same hash in the filename, we can reasonably assume they are the same.

[taralx]

Ah, I see the problem. Is it okay if I just rework the patch, or would you prefer I stack on top?

[taralx]

sigh This gets complicated again. I'll resubmit after I work this one out.