// Sanitize the range of a regular expression
// The cases are complicated, see test cases for details
const sanitizeRange = range => range.replace(
    REGEX_REGEXP_RANGE,
    (match, from, to) => from.charCodeAt(0) <= to.charCodeAt(0)
        ? match
        // Invalid range (out of order) which is ok for gitignore rules but
        //   fatal for JavaScript regular expression, so eliminate it.
        : EMPTY
)