gistfile1.js

  var fmh = merge(
    frontMatter.loadFront(e),
    {path: e}
  ); //=> 
  
  //{ date: Sun Aug 24 2014 17:00:00 GMT-0700 (PDT),
  //tags: 'log',
  //__content: '\n\nThis is my first post',
  //path: './_src/_blog/1/index.md' }
  
  var path_keys = path.relative('./_src/', e).split('/');//  => ['_blog', '1', 'index.md']

  var mid_hash = path_keys.reduceRight(function(p, c, i, a){
    var b={};
    b[c]=p;
    return b;
  }, fmh);


  console.log(mid_hash); // returns { _blog: { '1': { 'index.md': [Object] } } }