I just made a program which I call: Automatic Tree Farm.
This is also my first ComputerCraft program.
Note: It currently only works on birch, jungle and spruce saplings. As oak saplings have a chance of growing into a giant tree, it won't work.
Note: The bug where the turtle will do weird things when it runs out of saplings, bonemeal or fuel is now solved. However, you do need to place the exact same saplings, bonemeal and fuel (coal and charcoal are different items) in slots 14, 15 and 16. You only need 1 template item per slot. If you place the template items in the wrong order, or you don't even place them, the turtle will show a fake message saying it has run out of saplings, bonemeal or fuel.
If you didn't already guess, this is a fully automatic tree farm program. You need to give it saplings, bonemeal and some kind of fuel (coal, wood, lava, etc). The saplings go into the first slot, the bonemeal into the second slot and the fuel into the third slot. You now also need to place template items in slots 14, 15 and 16. The items must be exactly the same as the items the turtle is using. This is needed for the failsafe function. You only need 1 template item per slot. If you place the template items in the wrong order, or you don't even place them, the turtle will show a fake message saying it has run out of saplings, bonemeal or fuel. It currently only supports 1 stack of bonemeal, unfortunately.
How to install:
Be sure to leave feedback and report any bugs you encounter.
If you have questions feel free to ask them.
Also, if you have an idea on how it can support multiple (3 preferred) stacks of bonemeal, tell me.