fix: Reeds-Shepp headland turn

Use a Reeds-Shepp turn instead of the old combine
headland turn which used angles and relative
distances to steer the vehicle.

#786

Author: Peter Vaiko

scripts/Course.lua

@@ -915,13 +915,13 @@ function Course:extend(length, dx, dz)
     for i = first, last, step do
         local x = lastWp.x + dx * i
         local z = lastWp.z + dz * i
-        self:appendWaypoint({ x = x, z = z })
+        self:appendWaypoint({ x = x, z = z, rev = lastWp.rev })
     end
     if length % step > 0 then
         -- add the remainder to make sure we extend all the way up to length
         local x = lastWp.x + dx * length
         local z = lastWp.z + dz * length
-        self:appendWaypoint({ x = x, z = z })
+        self:appendWaypoint({ x = x, z = z, rev = lastWp.rev })
     end
     -- enrich the waypoints we added
     self:enrichWaypointData(nWaypoints)

scripts/CpUtil.lua

@@ -466,7 +466,7 @@ function CpUtil.getAllRootVegetables()
         local preparedGrowthState = fruitTypeData.preparedGrowthState
         local name = fruitTypeData.name
 
-        -- check if fruit is needs herb removement to be harvested
+        -- check if fruit is needs herb removal to be harvested
         if minPreparingGrowthState ~= -1 and preparedGrowthState ~= -1 and name ~= "SUGARCANE" then
 			local fruitType = g_fruitTypeManager:getFruitTypeByName(name)
             if fruitType ~= nil then

scripts/ai/turns/AITurn.lua

@@ -763,7 +763,7 @@ end
 function CombineHeadlandTurn:startTurn()
     self:debug('Starting a combine headland turn')
     self.turnCourse = ReedsSheppHeadlandTurn(self.vehicle, self.turnContext,
-            self.turnContext.vehicleAtTurnStartNode, self.turningRadius):getCourse()
+            self.vehicle:getAIDirectionNode(), self.turningRadius):getCourse()
     self.state = self.states.TURNING
     self.ppc:setCourse(self.turnCourse)
     self.ppc:initialize(1)

scripts/ai/turns/TurnManeuver.lua

@@ -565,6 +565,10 @@ function ReedsSheppHeadlandTurn:init(vehicle, turnContext, vehicleDirectionNode,
             turnContext.lateWorkStartNode, 0, -turnContext.backMarkerDistance, turningRadius)
     self.course = Course.createFromAnalyticPath(vehicle, path, true)
     self.course:adjustForReversing(2)
+    -- add a little straight section to the end so we have a little buffer and don't end the turn right at
+    -- the work start
+    self.course:extend(5)
+    TurnManeuver.setLowerImplements(self.course, 5, true)
 end
 
 ---@class TurnEndingManeuver : TurnManeuver