add 'config' entry point, pack.shared_file(...) & refactor engine_paths.cpp

doc/en/engine-use-recommendations.md

@@ -19,7 +19,8 @@ Content pack identifier requirements:
 
 ### Content packs data
 
-Settings and other state that supposed to be saved with a world, must be stored in `world:data/pack_id/`. The path should be retrieved by calling a function:
+State that supposed to be saved with a world, must be stored in `world:data/pack_id/`. The path should be retrieved by calling a function:
+
 ```lua
 local path = pack.data_file(PACK_ID, "file_name")
 file.write(path, some_data)
@@ -29,3 +30,13 @@ PACK_ID is an existing variable containing current content-pack name.
 
 Directory `world:data/PACK_ID` will be created on call `pack.data_file(...)`.
 
+#### Shared data
+
+Settings and other data that should be accessible from all worlds where the pack is used should be in
+`config:pack_id/`. You can use a special function:
+
+```lua
+local path = pack.shared_file(PACK_ID, "file_name")
+file.write(path, data)
+-- writes data to the file config:PACK_ID/file_name
+```

doc/en/scripting.md

@@ -47,14 +47,38 @@ pack.is_installed(packid: str) -> bool
 
 Check if specified pack is installed in the world
 
-```python
+```lua
 pack.data_file(packid: str, filename: str) -> str
+-- and
+pack.shared_file(packid: str, filename: str) -> str
 ```
 
-Returns data file path like `world:data/packid/filename` 
-and creates missing directories.
+Returns the path to the data file
+and creates missing directories in the path.
 
-Use this function when saving pack settings or other data to the world.
+- The first option returns: `world:data/packid/filename`
+- The second option returns: `config:packid/filename`
+
+Examples:
+```lua
+file.write(pack.data_file(PACK_ID, "example.txt"), text)
+```
+For a *containermod* pack, write text to `world:data/containermod/example.txt`.
+
+Use this to store in-world data.
+
+```lua
+file.write(pack.shared_file(PACK_ID, "example.txt"), text)
+```
+For a *containermod* pack, write text to `config:containermod/example.txt`
+
+Use this to store shared data for all worlds.
+
+```python
+pack.get_folder(packid: str) -> str
+```
+
+Returns the path to the folder of the installed content pack.
 
 Example:
 ```lua