Why cp a directory into itself still create an empty directory?

[Peng Yu]

Hi,

The following code shows that cp a directory into itself still create
the tmp directory in the destination. Is better not to create it?

/tmp$ mkdir tmp
/tmp$ $(type -P cp)  -r tmp tmp
/usr/local/opt/coreutils/libexec/gnubin/cp: cannot copy a directory,
‘tmp’, into itself, ‘tmp/tmp’
/tmp$ ls -lgd /tmp/tmp
drwxr-xr-x 3 wheel 102 Jun 14 11:05 /tmp/tmp

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Regards,
Peng