Rebuilding index.html with gulp-inject on scss file changes

gulp-watch-inject.js

'use strict';

var watch = require('gulp-watch'),
    inject = require('gulp-inject'),
    sass = require('gulp-sass'),
    gulp = require('gulp'),
    es = require('event-stream');

gulp.task('default', function () {
    watch({glob: 'sass/*.scss'}, function(scss) {
        // Compiling new and changed scss files
        var css = scss
            .pipe(sass())
            .pipe(gulp.dest('build'));

        // rebuilding index.html with gulp-inject
        return gulp.src('index.html')
            .pipe(inject(es.merge(css, gulp.src('build/*.css'))))
            .pipe(gulp.dest('build'));
    });
});