As referenced in this issue: https://github.com/janl/mustache.js/issues/562 Partials aren't indented as per the spec: https://github.com/mustache/spec/blob/master/specs/partials.yml#L13-L15 This adds indentation tracking for partials and applies them to the first instance of a partial on a line (to not indent inline partials which would violate a different part of the spec).