Gulp insert front-matter date from filename

gulpfile.js

// Throwaway Gulp script to insert dates from file-names into the front-matter
// of content source files

var gulp  = require('gulp'),
  through = require('through2');

gulp.task('insert-dates', function() {
  return gulp.src('content/posts/**/*.md')
    .pipe(through.obj(
      function(file, enc, callback) {
        var pathParts = file.path.split('/'),
          pathDate = pathParts[pathParts.length - 1].substr(0, 10);
        file.contents = new Buffer(String(file.contents).replace(
          /match line of front matter to insert date after/,
          'match line of front matter to insert date after\ndate: ' + pathDate
        ));
        return callback(null, file);
      })
    )
    .pipe(gulp.dest('content/posts'));
});