nixpkgs/pkgs/common-updater/scripts/list-archive-two-levels-versions

#!/usr/bin/env bash

# lists all available versions listed for a package in a site (http)

pname=""  # package name
attr_path=""  # package attribute path
url=""  # directory listing url
file=""  # file for writing debugging information

while (( $# > 0 )); do
    flag="$1"
    shift 1
    case "$flag" in
        --pname=*)
            pname="${flag#*=}"
            ;;
        --attr-path=*)
            attr_path="${flag#*=}"
            ;;
        --url=*)
            url="${flag#*=}"
            ;;
        --file=*)
            file="${flag#*=}"
            ;;
        *)
            echo "$0: unknown option ‘${flag}’"
            exit 1
            ;;
    esac
done

if [[ -z "$pname" ]]; then
    pname="$UPDATE_NIX_PNAME"
fi

if [[ -z "$attr_path" ]]; then
    attr_path="$UPDATE_NIX_ATTR_PATH"
fi

# by default set url to the base dir of the first url in src.urls
if [[ -z "$url" ]]; then
    url="$(nix-instantiate $systemArg --eval -E \
               "with import ./. {}; dirOf (dirOf (lib.head $attr_path.src.urls))" \
            | tr -d '"')"
fi

# print a debugging message
if [[ -n "$file" ]]; then
    echo "# Listing versions for '$pname' at $url" >> $file
fi

# list all major-minor versions from url
tags1=$(curl -sS "$url/")
tags1=$(echo "$tags1" | sed -rne 's,^<a href="([0-9]+\.[0-9]+)/">.*,\1,p')

# print available versions
for tag in $tags1; do
    tags2=$(curl -sS "$url/$tag/")
    tags2=$(echo "$tags2" | sed -rne "s,^<a href=\"$pname-([0-9.]+)\\.[^0-9].*\">.*,\\1,p")
    echo "$tags2"
done