gulpfile.js

var fs = require('fs');
var gulp = require('gulp');
var Server = require('karma').Server;
var concat = require('gulp-concat');
var jshint = require('gulp-jshint');
var header = require('gulp-header');
var footer = require('gulp-footer');
var rename = require('gulp-rename');
var es = require('event-stream');
var del = require('del');
var uglify = require('gulp-uglify');
var plumber = require('gulp-plumber');//To prevent pipe breaking caused by errors at 'watch'
var git = require('gulp-git');
var bump = require('gulp-bump');
var runSequence = require('run-sequence');
var versionAfterBump;

gulp.task('default', ['build', 'test']);
gulp.task('build', ['scripts']);
gulp.task('test', ['build', 'karma']);

gulp.task('watch', ['build', 'karma-watch'], function() {
    gulp.watch(['src/**/*.{js,html}'], ['build']);
});

gulp.task('clean', function(cb) {
    del(['dist'], cb);
});

gulp.task('scripts', ['clean'], function() {

    var buildLib = function() {
        return gulp.src(['src/*.js'])
                .pipe(plumber({
                    errorHandler: handleError
                }))
                .pipe(header('(function () { \n\'use strict\';\n'))
                .pipe(footer('\n}());'))
                .pipe(jshint())
                .pipe(jshint.reporter('jshint-stylish'))
                .pipe(jshint.reporter('fail'));
    };
    var config = {
        pkg: JSON.parse(fs.readFileSync('./package.json')),
        banner:
                '/*!\n' +
                ' * <%= pkg.name %>\n' +
                ' * <%= pkg.homepage %>\n' +
                ' * Version: <%= pkg.version %> - <%= timestamp %>\n' +
                ' * License: <%= pkg.license %>\n' +
                ' */\n\n\n'
    };

    return es.merge(buildLib())
            .pipe(plumber({
                errorHandler: handleError
            }))
            .pipe(concat('event.js'))
            .pipe(header(config.banner, {
                timestamp: (new Date()).toISOString(), pkg: config.pkg
            }))
            .pipe(gulp.dest('dist'))
            .pipe(uglify({preserveComments: 'some'}))
            .pipe(rename({extname: '.min.js'}))
            .pipe(gulp.dest('dist'));

});

gulp.task('karma', ['build'], function() {
    var server = new Server({configFile: __dirname + '/karma.conf.js', singleRun: true});
    server.start();
});

gulp.task('karma-watch', ['build'], function() {
    var server = new Server({configFile: __dirname + '/karma.conf.js', singleRun: false});
    server.start();
});

var handleError = function(err) {
    console.log(err.toString());
    this.emit('end');
};

gulp.task('release:bump', function() {
    var type = process.argv[3] ? process.argv[3].substr(2) : 'patch';
    return gulp.src(['./package.json'])
            .pipe(bump({type: type}))
            .pipe(gulp.dest('./'))
            .on('end', function() {
                versionAfterBump = require('./package.json').version;
            });
});

gulp.task('release:rebuild', function(cb) {
    runSequence('release:bump', 'build', cb); // bump will here be executed before build
});

gulp.task('release:commit', ['release:rebuild'], function() {
    return gulp.src(['./package.json', 'dist/**/*'])
            .pipe(git.add())
            .pipe(git.commit(versionAfterBump));
});

gulp.task('release:tag', ['release:commit'], function() {
    git.tag(versionAfterBump, versionAfterBump);
});

gulp.task('release', ['release:tag']);