Australian English has this... "yeah, nah" and "nah, yeah" are commonly used as replies to negative sentences. Well, all sentences really, but in this context negative ones.
"You've got no chance of beating that thing in a fight, mate" "yeah, nah" (I agree)
"Reckon it's never going to rain again?" "nah, yeah" (it will, eventually)
Your example of "no, yeah we're all out" doesn't actually work, because the "yeah" is dangling. The "yeah, no" works (the yeah agrees with the question, we do serve Pepsi, but the no modifies it because we're all out).
and the same for the "yeah, no" in the second example - the "no" is dangling.
but yeah, it can be confusing if the tone of the original question implies a negative (like "you don't serve Pepsi here do you?").
took me ages to work out that the first value doesn't matter ;)
We had yea/nay/yes/no. The former pair are not just 'olde' ways of saying latter; the equivalent of 'si' is actually 'yes', we just started using it for 'oui' too.
Hmm, not sure about that. Sydney here. I can't think offhand of a context where 'No, yeah' would have much meaning, if any. I never hear it. Does sound like bush talk, maybe, but not sure. e.g. "You don’t like me, do you?" "No, yeah" (or "yeah, no") would just be a meaningless, confusing response. You'd say "Yes! of course I do" or something.
There's that old joke where a lecturer is telling the audience about how two affirmatives never make a negative in English, and a voice is heard "Yeah yeah". I guess you could try "You don't like me, do you?" "No no, I do!". But whatever's said, the meaning would be determined mostly by the tone of voice, facial expression, body language etc
"You've got no chance of beating that thing in a fight, mate" "yeah, nah" (I agree)
"Reckon it's never going to rain again?" "nah, yeah" (it will, eventually)