Thanks! I found him finally. I killed the two raiders that were sort of surrounding him and tried speaking with the dog. Using google translate I found out that the message that appeared above the dog when you try and talk to him amounts to "grrr". I tried giving him some beef jerky but nothing came of it. I really have no idea what I need to do to progress further... Unless he's not meant at all to join you, which is strange since it seems like it's a brand new model.
EDIT: I got him! I'm an idiot... I was feeding him beef jerky when the original Dogmeat from Fallout 1 eats an Iguana on a stick... So that's what you have to give him
I fed him an iguana-on-a-stick and I started talking with him. I have no idea what the text says but I chose the first option if I recall correctly and he joined my party.
Also, I have no idea if it influences or not but in the original Fallout, you had to feed the iguana OR wear a leather jacket when talking to Dogmeat (reference to Mad Max in Road Warrior), coincidently, I was wearing a leather jacket when I fed the iguana on a stick to the Dog in Reno. No idea if you have to do both or just feed him.