func parseVersion(v string) (maj, min int, tail string) {
        if i := strings.Index(v, "beta"); i > 0 {
                tail = v[i:]
                v = v[:i]
        }
        if i := strings.Index(v, "rc"); i > 0 {
                tail = v[i:]
                v = v[:i]
        }
        p := strings.Split(strings.TrimPrefix(v, "go1."), ".")
        maj, _ = strconv.Atoi(p[0])
        if len(p) < 2 {
                return
        }
        min, _ = strconv.Atoi(p[1])
        return
}

func versionLess(a, b string) bool {
        // Put stable releases first.
        if isStable(a) != isStable(b) {
                return isStable(a)
        }
        maja, mina, ta := parseVersion(a)
        majb, minb, tb := parseVersion(b)
        if maja == majb {
                if mina == minb {
                        return ta >= tb
                }
                return mina >= minb
        }
        return maja >= majb
}

                        if len(unstable) != 0 {
                                // Only show one (latest) unstable version,
                                // consider the older ones to be archived.
                                archive = append(archive, *r)
                                return
                        }