It would be great to have a little bit of meta data included in the JSON exports so I can quickly validate that the JSON file being imported is in fact Spine data. Also maybe the version of Spine it was created with.

example of TexturePacker's meta block:

"meta": {
   "app": "http://www.texturepacker.com",
   "version": "1.0",
   "image": "DudeCell.png",
   "format": "RGBA8888",
   "size": {"w":512,"h":1024},
   "scale": "0.5",
   "smartupdate": "$TexturePacker:SmartUpdate:1a3e06660e6f9855aca66037128ecde4$"
}

(note they also have a hash to determine whether anything has changed and needs to be updated)

Can't attach *.cs files apparently... but here ya go.

using UnityEngine;
using UnityEditor;
using System.Collections;
using System.IO;
using System.Text;
using Spine;

public class SpineIngestHelper {
   const float defaultMix = 0.2f;
   const string defaultShader = "Spine/Skeleton";
   

   [MenuItem("Assets/Ingest/Spine Project")]
   static void IngestSpineProject(){
      TextAsset spineJson = null;
      TextAsset atlasText = null;
      

  foreach(UnityEngine.Object o in Selection.objects){
     if(o.GetType() != typeof(TextAsset))
        continue;
     
     string fileName = Path.GetFileName(AssetDatabase.GetAssetPath(o));
     
     if(fileName.EndsWith(".json"))
        spineJson = (TextAsset)o;
     else if(fileName.EndsWith(".atlas.txt"))
        atlasText = (TextAsset)o;
  }
  
  if(spineJson == null){
     EditorUtility.DisplayDialog("Error!", "Spine JSON file not found in selection!", "OK");
     return;
  }
  
  string primaryName = Path.GetFileNameWithoutExtension(spineJson.name);
  string assetPath = Path.GetDirectoryName( AssetDatabase.GetAssetPath(spineJson));
  
  if(atlasText == null){
     string atlasPath = assetPath + "/" + primaryName + ".atlas.txt";
     atlasText = (TextAsset)AssetDatabase.LoadAssetAtPath(atlasPath, typeof(TextAsset));
  }
  
  if(spineJson != null && atlasText != null){
     
     
     
     AtlasAsset atlasAsset = AtlasAsset.CreateInstance<AtlasAsset>();
     atlasAsset.atlasFile = atlasText;
     
     atlasAsset.materials = new Material[1];
     string materialPath = assetPath + "/" + primaryName + "_Material.mat";
     Material mat = new Material(Shader.Find(defaultShader));
     
     string[] atlasLines = atlasText.text.Split(new char[2]{'\r', '\n'}, System.StringSplitOptions.RemoveEmptyEntries);
     string texturePath = assetPath + "/" + atlasLines[0];
     
     Texture2D texture = (Texture2D)AssetDatabase.LoadAssetAtPath(texturePath, typeof(Texture2D));
     
     TextureImporter texImporter = (TextureImporter)TextureImporter.GetAtPath(texturePath);
     texImporter.textureFormat = TextureImporterFormat.AutomaticTruecolor;
     texImporter.mipmapEnabled = false;
     AssetDatabase.SaveAssets();
     
     mat.mainTexture = texture;
     
     AssetDatabase.CreateAsset(mat, materialPath);
     AssetDatabase.SaveAssets();
     
     atlasAsset.materials[0] = mat;
     
     AssetDatabase.CreateAsset(atlasAsset, assetPath + "/" + primaryName + "_Atlas.asset");
     AssetDatabase.SaveAssets();
     
     SkeletonDataAsset skelDataAsset = SkeletonDataAsset.CreateInstance<SkeletonDataAsset>();
     skelDataAsset.atlasAsset = atlasAsset;
     skelDataAsset.skeletonJSON = spineJson;
     skelDataAsset.fromAnimation = new string[0];
     skelDataAsset.toAnimation = new string[0];
     skelDataAsset.duration = new float[0];
     skelDataAsset.defaultMix = defaultMix;
     
     AssetDatabase.CreateAsset(skelDataAsset, assetPath + "/" + primaryName + "_SkeletonData.asset");
     AssetDatabase.SaveAssets();
  }
  else{
     EditorUtility.DisplayDialog("Error!", "Atlas file not found in selection!", "OK");
     return;
  }
   }
}