boost_cart API
==============

This file provides information about the API of boost_cart for the use in
mods. The API might change slightly when the development goes on, so avoid
using internal tables or functions which are not documented here.


Types
-----

* `SwitchIgnore` -> `number/nil`
	* Specifies which player control was pressed. This value is used to prefer
	  straight rails instead of preferring left and right rail checks.
		* `1`: Ignore left rail
		* `2`: Ignore right rail
		* `nil`: Ignore no rail


Entity movement
---------------
These functions are grouped so that they make sense and then sorted alphabetically.

* `boost_cart:manage_attachment(player, obj)`
	* Attaches or detaches the player to/from an object, depending on what is
	  supplied to `obj`.
	* `player`: `ObjectRef` of the player
	* `obj`: `ObjectRef` (to attach) or `nil` (to detach)
* `boost_cart:get_sign(n)` -> `number`
	* Returns the sign for the given number. Values: `-1`, `0`, `1`
	* `n`: any `number`
* `boost_cart:velocity_to_dir(vel)` -> `vector`
	* Returns the cart direction depending on `vel`. Each coordinate can have
	  one of the `get_sign()` return values.
	* `vel`: velocity as `vector`
* `boost_cart:boost_rail(pos, amount)`
	* Sets the rail acceleration for the given position to `amount` and punches
	  carts which are at the given position.
	* `pos`: `vector`, rail position
	* `amount`: `number`, negative to brake, positive to boost
* `boost_cart:get_rail_direction(pos, dir, ctrl, old_switch, railtype)`
	-> `vector, SwitchIgnore`
	* Returns the direction to where the next rail is, and which player control that
	  should be ignored in the next call.
	* `pos`: `vector`, position of the cart
	* `dir`: `vector`, movement direction of the cart (see `velocity_to_dir()`)
	* `ctrl`: Player controls table or `nil` (no player)
	* `old_switch`: `SwitchIgnore`
	* `railtype`: (optional) `number`, gets passed indirectly to `is_rail()`


Rail helper functions
---------------------
* `boost_cart:get_rail_groups(groups)` -> `table`
	* Returns a group table with preset values for a common rail node
	* `groups`: (optional) `table`, additional groups append (or overwrite)
	* Hint: To register an incompatible rail type, set the group
	  `connect_to_raillike` to the value returned by
	  `minetest.raillike_group(new_rail_type)`
* `boost_cart:is_rail(pos, [railtype])` -> `boolean`
	* Returns whether the node at `pos` is a rail. When `railtype` is specified,
	  `true` is only returned when the node is in the same rail group.
	* `pos`: `vector` of the node to check
	* `railtype`: (optional) `number`, rail group number
* `boost_cart:register_rail(name, def)`
	* Registers a new rail with preset node definition defaults as fallback
	* `name`: `string`, node name of the new rail
	* `def`: Node definition table, containing at least the following keys:
		* `description`
		* `groups`
		* `tiles`