R27 Bugs

[instafluff0]

Thanks so much for all the time and work you put into, well, everything for R27. I followed the commits and don't know what the heck was up with the infinite loop with Aerodromes, as I had that code activated before, saw AIs moving air units to Aerodromes, and never ran into it. I'm not sure if it was an artifact of the merge or what. Anyway sorry you had to fix that.

On the other points, I have on one occasion seen AIs build canals. I'll make time when I'm back to figure out what's up.

More important though I think is the transport loading issue. I never noticed that and that seems like a pretty high priority I'll try to figure out.

[instafluff0]

A quick review (I have to literally head out the door soon) makes me think we need to patch Unit::find_transport and possibly repl call Tile::has_city before that, as I see that potentially gating the find_transport calls in Unit::ai_move_offensive_unit, Unit::ai_move_settler, Unit::ai_go_to_capital and maybe others.

[maxpetul]

Thanks so much for all the time and work you put into, well, everything for R27.

Sure thing. It's a labor of love, at least most of the time. Frankly I've been feeling somewhat burned out working on C3X recently so I'm glad to have something released finally.

By the way, there's another smaller issue with ports in that the AI struggles to build them. In my test games watching the AI, it took I estimate at least 100 turns before any ports appeared on the map. The AI was sometimes queueing up naval units in its port-less cities. None of those builds completed, as expected, as they were switched to land units instead. The AI didn't go on to build ports for those cities where it wanted to build naval units, though, so either no request was created for one or it wasn't fulfilled for some reason. The AI does build ports eventually, I believe in connection to trying to build harbors. Perfuming harbors might help as a workaround for this issue but I haven't tested that.

[maxpetul]

The first bug report has come in: The button to build canals appears even when enable_canal_districts is false; there is a missing check for that setting in can_build_district_on_tile. Also I checked whether setting max_contiguous_canal_districts to zero would remove the button, and it did not. That feels like another bug.

Edit: Almost forgot, the person also reported that canals were available to build at the start of the game so the tech prereq might not be getting applied either.