The Science of Household Tips: Does vinegar actually set dye in jeans?

When I bought my latest pair of jeans, the nice lady who helped me find them advised me to wash them with a cup of vinegar the first time, to better set the dye. I didn't think much of it, until I wore the jeans before washing them and ended up with mildly blue thighs. So clearly pre-washing would have been a good idea, but.. does vinegar actually set dye?

Googling this mostly turned up a bunch of people parroting the same tip. Which would be reassuring if I didn't know that the internet is a sucker for feasible-sounding tips regardless of they make sense or work. (Witness: Pinterest vs Pinstrosity)

My research turned up the following claims, from the ever-reputable source of "people on the internet"

1. Vinegar totally helps set dye in jeans
2. Vinegar totally helps set dye... but not in cotton, so you're wasting your time with jeans.
3. For jeans, you should really use salt, not vinegar
4. Actually, you shouldn't wash jeans at all
5. It doesn't matter, but for the love of all that is blue, wash your jeans in cold water
6. You need to wash your jeans inside-out
7. Mine totally leaked dye so I gave them away and bought new ones!

But 0% of these came with sources that gave me any indication if these were really legit or just old wives tales. I don't need scientific journal papers, but you'd think there'd at least be a science fair project or tests from some sort of cross between consumer reports and good housekeeping.

So where do you go for figuring out if there's actually any proof behind household tips like this?