forum.freeciv.org

Please correct me: So far I think that ruleup 3.0 can read a 2.6 ruleset, and save it in a format suited for 3.0; approximating the old 2.6 behaviour as far as possible with new 3.0 features. That would be great, but presumably unsuited for a quick line-oriented diff to see what was changed.

An additional dummy ruleup 2.6 converting any working 2.6 ruleset to an equivalent 2.6 ruleset in "ruleup 2.6 format" could allow a diff with a 3.0 ruleset in a very similar "ruleup 3.0 format".

Just loading and saving a ruleset in ruledit should suffice. I don't think it likely that we backport all the things ruleup depends on to 2.6.