boostrap theming -- How to remove duplicate styles?

This question is less of a code question and more of a best-practices question. I am working on a custom bootstrap theme based on https://github.com/HackerThemes/theme-kit. I have a working theme that I like, however, I am overriding some styles in the original Bootstrap theme. Even in the minified CSS, these are duplicated. For example, Bootstrap defines...

.btn-danger:hover {
    color: #fff;
    background-color: #ae130b;
    border-color: #a2120a;
}

...but my code also defines...

.btn-danger:hover {
    border-color: #0000;
}

In the final stylesheet, both of these styles are present. The second style overrides Bootstrap and it looks just fine. However, this leads to useless code. First of all, is there a postprocessor of some sort that I can use with Gulp to eliminate these duplicates and consolidate them? Second, should I just fork the Bootstrap repository and modify the original SCSS directly?

It depends on what you @import. Looking at mytheme.scss, the entire Bootstrap SASS is imported, creating full duplicate code in the final CSS.

Instead you can pick specific SASS files to import and look at the option variables which also effects what CSS is generated. For example, setting $enable-grid-classes: false will prevent duplication of the entire grid system in the generated CSS.