Make refuelling a little more flexible

This removes the link between item size and refuel limit, meaning
working with other items (such as FE items) is a little easier.

src/main/java/dan200/computercraft/shared/turtle/apis/TurtleAPI.java

@@ -303,7 +303,8 @@ public class TurtleAPI implements ILuaAPI
             case 31:
             {
                 // refuel
-                int count = parseCount( args, 0 );
+                int count = optInt( args, 0, Integer.MAX_VALUE );
+                if( count < 0 ) throw new LuaException( "Refuel count " + count + " out of range" );
                 return tryCommand( context, new TurtleRefuelCommand( count ) );
             }
             case 32:

src/main/resources/assets/computercraft/lua/rom/programs/turtle/refuel.lua

@@ -6,19 +6,27 @@ if #tArgs > 1 then
     return
 elseif #tArgs > 0 then
     if tArgs[1] == "all" then
-        nLimit = 64 * 16
+        nLimit = nil
     else
         nLimit = tonumber( tArgs[1] )
+        if not nLimit then
+            print("Invalid limit, expected a number or \"all\"")
+            return
+        end
     end
 end
 
 if turtle.getFuelLevel() ~= "unlimited" then
     for n = 1, 16 do
+        -- Stop if we've reached the limit, or are fully refuelled.
+        if (nLimit and nLimit <= 0) or turtle.getFuelLevel() >= turtle.getFuelLimit() then
+            break
+        end
+
         local nCount = turtle.getItemCount(n)
-        if nLimit > 0 and nCount > 0 and turtle.getFuelLevel() < turtle.getFuelLimit() then
+        if nCount > 0 then
-            local nBurn = math.min( nLimit, nCount )
             turtle.select( n )
-            if turtle.refuel( nBurn ) then
+            if turtle.refuel( nLimit ) and nLimit then
                 local nNewCount = turtle.getItemCount(n)
                 nLimit = nLimit - (nCount - nNewCount)
             end