Trade routes should not yield 0
ddeanbrown Even route with 0 trade (e.g. after city size has shrunk) has the benefit of keeping the route alive, for the time when the trade increases. Making 1 the minimum trade would mean that there's no benefit of developing the city (or even the route -> distance) to level where it would really deserve that 1 trade. This can be significant in a low-trade ruleset.
Overall, I don't think either making 1 the minimum trade or keeping the current behavior is correct for all situations / rulesets. Should we make it a ruleset setting?
ddeanbrown As this is really affecting people, and is sort of bugfix support for the rulesets, not just a new feature, I think we can still add this to S3_1 d3f.
Because of round down, a trade route can give 0 trade, should have minimum of 1.