To update a tileset from 2.6 to 2.90.99 (will be 3.0 in the future) you must add some new graphics and update the file format strings. Currently these instructions go up to compatibility with freeciv revision 28756.
The .tilespec file
- Set format of .tilespec file to options = "+Freeciv-tilespec-Devel-YYYY.MMM.DD" during development. For freeciv 3.0 options = "+Freeciv-3.0-tilespec" should be used.
- minimap_intro_file (also called the 'radar graphics') is no longer mandatory part of the tileset. Only the (currently unmaintained) xaw-client uses that gfx, and even it can live without it. Simply leave minimap_entry_file entry out from the tilespec if you don't want it.