jekyll and gulp

gulpfile.js

var gulp = require('gulp');
var sass = require('gulp-sass');
var livereload = require('gulp-livereload');
var prefix = require('gulp-autoprefixer');
var sourcemaps = require('gulp-sourcemaps');
var runSequence = require('run-sequence');

gulp.task('sass', function () {
    gulp.src('./assets/css/*.scss')
        .pipe(sourcemaps.init())
        .pipe(sass(
            {
            outputStyle: 'compressed',
            sourceComments: 'map',
            errLogToConsole: true,
            includePaths: ['./_sass']
            }
        ))
        .pipe(prefix("last 4 version"))
        .pipe(sourcemaps.write('./maps'))
        .pipe(gulp.dest('./_site/assets/css/'))
        .pipe(livereload());
});

gulp.task('watch', function() {
    livereload.listen();
    gulp.watch('./assets/css/*.{scss,sass}', ['sass']);
    gulp.watch('./_sass/*.{scss,sass}', ['sass']);
    gulp.watch('./assets/**/*.{js,png,jpg}', ['build']);
    gulp.watch('./*.html', ['build']);

});

// The default task (called when you run `gulp` from cli)
gulp.task('default', ['watch'], function(){
    var spawn = require('child_process').spawn;
    var jekyll = spawn('jekyll', ['serve', '--no-watch'], {stdio: 'inherit'});

});

gulp.task('jekyll-build', function (gulpCallBack){
    var spawn = require('child_process').spawn;
    var jekyll = spawn('jekyll', ['build'], {stdio: 'inherit'});
 
    jekyll.on('exit', function(code) {
         gulpCallBack(code === 0 ? null : 'ERROR: Jekyll process exited with code: '+code);
    });
});

gulp.task('build', function(callback){
    runSequence('jekyll-build',
              ['sass'],
              callback);
});