gulp.watch('watch', function() {
 watch('./app/index.html', function() {
  gulp.start('html');
 });
});

var gulp = require("gulp"),
    watch = require('gulp-watch');

gulp.task('default', function(done){
  console.log("You created the default task");
  done();``
});

gulp.task('html', function(done){
  console.log('modifying the html');
  done();
});

gulp.watch('watch', function() {
 watch('./app/index.html', function() {
  gulp.start('html');
 });
});