static getLiteral(segment) {
        let literal = '';
        for (let i = 0; i < segment.length; i++) {
            const c = segment[i];
            // Escape
            if (c === '\\' && !IS_WINDOWS && i + 1 < segment.length) {
                literal += segment[++i];
                continue;
            }
            // Wildcard
            else if (c === '*' || c === '?') {
                return '';
            }
            // Character set
            else if (c === '[' && i + 1 < segment.length) {
                let set = '';
                let closed = -1;
                for (let i2 = i + 1; i2 < segment.length; i2++) {
                    const c2 = segment[i2];
                    // Escape
                    if (c2 === '\\' && !IS_WINDOWS && i2 + 1 < segment.length) {
                        set += segment[++i2];
                        continue;
                    }
                    // Closed
                    else if (c2 === ']') {
                        closed = i2;
                        break;
                    }
                    // Otherwise
                    else {
                        set += c2;
                    }
                }
                // Closed?
                if (closed >= 0) {
                    // Cannot convert
                    if (set.length > 1) {
                        return '';
                    }
                    // Convert to literal
                    if (set) {
                        literal += set;
                        i = closed;
                        continue;
                    }
                }
                // Otherwise fall thru
            }
            // Append
            literal += c;
        }
        return literal;
    }
Attempts to unescape a pattern segment to create a literal path segment.
Otherwise returns empty string.