Q. How can I perform a quiet Windows 10 upgrade?
A. Behind the scenes of a Windows 10 upgrade that requires no input is really one command:
setup.exe /auto upgrade /quiet
There are other switches that can be used to supplement the upgrade process (as documented at http://blogs.technet.com/b/home_is_where_i_lay_my_head/archive/2015/09/14/windows-10-setup-command-line-switches.aspx) however the command above will perform a quiet upgrade to Windows 10 with no user prompts and will reboot automatically.