meaning of "auto ref const"?

[Picaud Vincent via Digitalmars-d-learn]

On Sunday, 18 December 2016 at 14:25:04 UTC, Basile B. wrote:
> ...
> As you can see, auto ref is more flexible with the parameter. 
> This make sense for templated functions.

Thank you for your detailed answer, things are perfectly clear 
now. Also sorry for the doc linksI should have found it before 
asking my question.