grunt-handlebars-inline-partials.js

handlebars : {
  options : {
    processAST: function(ast) {
        var Handlebars = require('handlebars');
        ast.statements.forEach(function(statement, i) {
          if (statement.type === 'partial') {
            var partialFile = grunt.util._.find(grunt.task.current.files, function (file) {
                return file.src[0].indexOf(statement.partialName.name) !== -1;
            });
            if (partialFile) {
                var parsed = Handlebars.parse(grunt.file.read(partialFile.src[0]));
                ast.statements.splice.apply(ast.statements, [i, 1].concat(parsed.statements));
            }
          }
        });
        return ast;
    }
    // ...
  }
  // ...
}