Bug#932990: freeciv: railroad and transformation in adjacent tiles

[Jacob Nevins]

David Christensen writes:
> Please see attached game save file freeciv-T0202-Y01510-manual.sav.bz2:

(This save game was created with Freeciv 2.5.6, using the 'classic'
ruleset.)

> 1.  Swamp near Kobenhavn with roads being upgraded to railroads.

I assume this is the tile highlighted if you paste
[l tgt="tile" x=37 y=12 /]
into the chatline.

> 2.  Adjacent swamp tile being transformed to swamp.

I assume this is [l tgt="tile" x=36 y=11 /], where *Ocean* is being
transformed to Swamp.

> When "Turn Done" is pressed:
> 
> 1.  Swamp is converted to ocean (bug).
> 
> 2.  Ocean is converted to swamp (correct).
> 
> 3.  Grassland adjacent to both of the above is converted to ocean (bug).

The unwanted terrain transformations are by design. Due to pollution,
catastrophic climate change has led to terrain changes. See Cities /
Pollution in the built-in help.

On the Messages tab after pressing Turn Done, I have among others these
messages:
| Global warming has occurred!
| Coastlines have been flooded and vast ranges of grassland have become deserts.

On the previous turn, the user interface shows:
| Shows the progress of global warming:
| Pollution rate: 5%
| Chance of catastrophic warming each turn: 14%

(In the Gtk client, this is shown as a tooltip for the 'sun' icon.)

(If you don't like this rule, you can turn it off in the server
settings for future games:
Game / Options / Remote server / Geological / Global warming
or '/set globalwarming disabled' from the server command line.
However, once a game has started, this option can't be changed.)