Tileset JSON: deprecate additional_tiles key and move contents into multitile key

[int-ua]

Is your feature request related to a problem? Please describe.

If "multitile": true always requires additional_tiles key to be present they can be simply merged, I don't see a need to have them both.

Describe the solution you'd like

Move contents of additional_tiles into multitile value, don't check if multitile is true but if it's present at all. Maybe I'll try to do that later but I already have a lot of other things to do.

Suggestion from @anothersimulacrum :

diff --git a/src/cata_tiles.cpp b/src/cata_tiles.cpp
index fed4154888..0088cd2ee6 100644
--- a/src/cata_tiles.cpp
+++ b/src/cata_tiles.cpp
@@ -919,12 +919,12 @@ void tileset_loader::load_tilejson_from_file( const JsonObject &config )
         for( const std::string &t_id : ids ) {
             tile_type &curr_tile = load_tile( entry, t_id );
             curr_tile.offset = sprite_offset;
-            bool t_multi = entry.get_bool( "multitile", false );
+            bool t_multi = entry.has_array( "multitile" );
             bool t_rota = entry.get_bool( "rotates", t_multi );
             int t_h3d = entry.get_int( "height_3d", 0 );
             if( t_multi ) {
                 // fetch additional tiles
-                for( const JsonObject subentry : entry.get_array( "additional_tiles" ) ) {
+                for( const JsonObject subentry : entry.get_array( "multitile" ) ) {
                     const std::string s_id = subentry.get_string( "id" );
                     const std::string m_id = t_id + "_" + s_id;
                     tile_type &curr_subtile = load_tile( subentry, m_id );
@@ -933,8 +933,6 @@ void tileset_loader::load_tilejson_from_file( const JsonObject &config )
                     curr_subtile.height_3d = t_h3d;
                     curr_tile.available_subtiles.push_back( s_id );
                 }
-            } else if( entry.has_array( "additional_tiles" ) ) {
-                entry.throw_error( "Additional tiles defined, but 'multitile' is not true." );
             }
             // write the information of the base tile to curr_tile
             curr_tile.multitile = t_multi;

It would also require changing compose.py, TILESET.md and tile_config.jsons if done in a backward-incompatible way.

Describe alternatives you've considered

Additional context

https://discord.com/channels/598523535169945603/598535887801810944/790871379821068308

[int-ua]

There was a suggestion here that was moved to #46835

[actual-nh]

Perhaps the "Documentation" label should be updated with a Tiles-related one?

[int-ua]

#46835

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions. Please do not 'bump' or comment on this issue unless you are actively working on it. Stale issues, and stale issues that are closed are still considered.

[Night-Pryanik]

Closing as stale, since stalebot can't do this by itself.