git-add-fork-remotes.js

/* Usage:
 * First, open https://github.com/[username]/[reponame]/network/members page of upsteam repo
 * After that open DevTools (normally F12), and then REPL (Esc), and copy-paste this there + hit Enter
 * Script will output a command for adding git remotes to your local repo, copy-paste that to your terminal
 */
function get_add_forks_cmd() {
  let main_fork_slug = prompt('Enter [username]/[reponame] slug please:')

  let fork_slugs = $x('//*[@id="network"]/div/a[2]/@href').
    map(h => h.value.slice(1))

  let fork_map = fork_slugs.
    map((f) => [f.slice(0, f.indexOf('/')), f])

  let target_forks_map = fork_map.
    filter(([f, s]) => f != main_fork_slug)

  let git_remote_cmds = target_forks_map.
    map(([f, s]) => 'git remote add ' + f + ' git://github.com/' + s + '.git')

  let git_add_forks_cmd = git_remote_cmds.join('; ')
  return git_add_forks_cmd
}

console.log(get_add_forks_cmd())