Category filter for Craft Cms searchit plugin. Takes nesting of categories into account. More information on http://craftsnippets.com/articles/filtering-entries

searchit_category_filter.twig

{% set handle = 'category_handle' %}
{% for category in craft.categories.group(handle).all() %}
{% set line = '' %}
{% set depth = category.getAncestors()|length %}
{% for number in range(0, depth) %}
{% set line = line ~ '=' %}
{% endfor %}
    {{ ({
        filter: {
            relatedTo: category.id
        },
        label: line ~ ' ' ~  category.title
    })|json_encode() }}{{ not loop.last ? ',' }}
{% endfor %}