I found lots of tabs in HTML files. As a result, when I indent with spaces, the diff looks all wrong (example: #590) though it does not break anything because HTML and JS do not care about indentation.

If I replace tabs with 4 spaces, the diff is going to be horrible, so I am opening an issue for discussion instead of PR. If you don't think this is worth doing, please close the issue as won't fix. Thanks.