bug#61386: [PATCH] cp,mv,install: Disable sparse copy on macOS

[Paul Eggert]

On 2/10/23 10:58, Pádraig Brady wrote:
> I was considering "touch"ing the timestamps after also,
> but it's better to just maintain them as we're
> pointing to the same data after all.

For POSIX conformance we must touch if the user has specified only POSIX 
options (and has not specified -p).

And it's not just a POSIX conformance issue. Ordinary users will be 
surprised if plain 'cp A B' creates a file B with a timestamp from last 
year.

Likewise for B's modes.

There's another complication: recent macOS versions have CLONE_ACL, and 
we're not using that.