tabler/build/unused-files.js

const glob = require("glob"),
  fs = require("fs");

let foundFiles = [];

glob.sync("pages/**/*.{html,md}").forEach(function (file) {
  let fileContent = fs.readFileSync(file);

  fileContent.toString().replace(/\{% include(_cached)? ([a-z0-9\/_-]+\.html)/g, function(f, c, filename){
    filename = 'pages/_includes/' + filename;

    if(!foundFiles.includes(filename)) {
      foundFiles.push(filename);
    }
  });
});

let includeFiles = glob.sync("pages/_includes/**/*.html");

includeFiles.forEach(function(file){
  if(! foundFiles.includes(file)) {
    console.log('file', file);
  }
});

// console.log('foundFiles', foundFiles);
// console.log('includeFiles', includeFiles);