Comment by sandinmyjoints

I looked up `-c` on macOS. It says it causes cp to use clonefile(2) instead of copyfile. So I looked up clonefile(2). It says:

    NAME
         clonefile – create copy on write clones of files
    
    SYNOPSIS
    ...
    
    LIMITATIONS
         Cloning directories with these functions is strongly discouraged.  Use copyfile(3) to clone directories instead.
    

But no explanation of why strongly discouraged.