RFR: 8264744: (fs) Use file cloning in Linux and macOS versions of FileChannel transfer and Files copy methods [v7]

[Brian Burkhalter]

On Fri, 12 Aug 2022 15:01:49 GMT, Brian Burkhalter <bpb at openjdk.org> wrote:

>>> On macOS it's not possible to clone using file descriptors; paths are required.
>> 
>> I understand that but what isn't clear is if the attributes are cloned too.  It might be that we only use it when not copying attributes.
>
> Right, I have some more investigation to perform here.

Based on my testing, attributes appear to be cloned by default except for the permission on linux-aarch64 and the (group) ownership on macosx-x64. If we want to suppress that behavior, then using clone would have to be made conditional.

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PR: https://git.openjdk.org/jdk/pull/9486