An Editor script that speeds up delivery of code-heavy workshops. It that allows to pull different versions of the code directly inside the Unity Project, by selecting a step from the top bar menu.

InjectionTool.cs

using UnityEngine;
using UnityEngine.UI;
using System.Collections;
using UnityEditor;
using UnityEditor.SceneManagement;
using System;
using System.IO;

public class InjectionTool : MonoBehaviour
{
	// These provide the name of the source and destination script folders
	static string versionedScriptsFolder = "Sources/Step";
	static string destinationScriptsFolder = "Assets/Scripts";
	static string currentLocation;
	static bool isRootFolder;

	const string menuName = "Code Version"; //the name of the menu item at the top


	#region MENU ITEMS

	// Example method to load a version of the code
	// Note that you will need to manually duplicate these methods for as many steps as you need
	[MenuItem(menuName + "/Step 0 - The Beginning")]
	static public void StepZero()
	{
		Version(0);

		//you can put custom actions here that modify the scene to show the version that was just loaded?
		GameObject.FindObjectOfType<Text>().text = "Version 0";
	}

	[MenuItem(menuName + "/Step 1 - Something is Moving")]
	static public void StepOne()
	{
		Version(1);

		GameObject.FindObjectOfType<Text>().text = "Version 1";
	}

	/*
	// Example method to load a version of a scene
	[MenuItem(menuName + "/Scene Version/Step 0")]
	static public void SceneOne()
	{
		EditorSceneManager.OpenScene("Assets/Scenes/EmptyScene.unity", OpenSceneMode.Single);
	}
	*/

	#endregion


	#region FUNCTIONALITY

	// This method is called by all code versioning methods above
	// It scans the Sources folder for all .cs files, and puts them into the Scripts folder
	// Sources and Scripts folder names are taken from the variables at the beginning of this file
	static private void Version(int stepNumber)
	{
		DirectoryInfo directoryInfo;
		FileInfo[] fileInfoArray;

		isRootFolder = true;

		//1: delete the files in the destination to clean the step, in case the user is going back in the history
		directoryInfo = new DirectoryInfo(destinationScriptsFolder);
		fileInfoArray = directoryInfo.GetFiles();
		DirectoryInfo[] dirs = directoryInfo.GetDirectories();
		foreach(FileInfo f in fileInfoArray)
		{
			f.Delete();
		}
		foreach(DirectoryInfo d in dirs)
		{
			d.Delete(true); //delete all sub-directories recursively
		}

			
		//2: write the files from the source folder to the destination
		directoryInfo = new DirectoryInfo(versionedScriptsFolder + stepNumber);
		currentLocation = destinationScriptsFolder; //start from the Scripts folder in Assets
		CopyFolder(directoryInfo);

		//3: force a recompile
		AssetDatabase.Refresh();
	}


	// This method scans a directory, copies all the files, then does the same for each sub-directory found
	static private void CopyFolder(DirectoryInfo directoryInfo)
	{
		//Debug.Log("Scanning " + directoryInfo.Name);
		string currentSubDir;

		//create the directory (only if it's not the root directory)
		if(isRootFolder)
		{
			currentSubDir = currentLocation;
			isRootFolder = false;
		}
		else
		{
			currentSubDir = currentLocation + "/" + directoryInfo.Name;
			Directory.CreateDirectory(currentSubDir);

			//Debug.Log("Created " + currentSubDir);
		}

		//copy all the files in the new destination
		FileInfo[] fileInfoArray = directoryInfo.GetFiles();
		foreach (FileInfo f in fileInfoArray)
		{
			if(f.Extension == ".cs")
			{
				//read source file
				StreamReader sr = File.OpenText(f.FullName);
				string contents = sr.ReadToEnd();
				sr.Close();

				//write in the destination file
				//(will be created if it doesn't exist)
				string destinationPath = currentSubDir + "/" + f.Name;
				StreamWriter sw = new StreamWriter(destinationPath);
				sw.Write(contents);
				sw.Close();

				//Debug.Log("Copied " + f.FullName + " to " + destinationPath);
			}
		}

		//recursive call for each directory included in this one
		DirectoryInfo[] dirs = directoryInfo.GetDirectories();
		foreach(DirectoryInfo d in dirs)
		{
			CopyFolder(d);
		}

		currentLocation = currentSubDir;
	}

	#endregion
}