Up to half a dozen or more carefully located - inside the guitar, taken from acoustic and mag pickups, and well as mics of various types located at various distance and heights located at various places within 360 degrees or even behind the player - signal inputs may be used by some guitarists. And then they start mixing, processing, and multitracking...

Now in the old days, you just sang into a tin can...

Then it was just musicianship: now it's more Art than Science, depending on what the guy playing with (and paying for) all the gadgets wants to achieve...