Add function to request latest github tag

config/config.rb.example

@@ -3,5 +3,6 @@
 CONFIG = {
   remote_path: 'example.com:/srv/httpd/some/path',
   download_url: 'https://example.com/some/path',
-  branch: 'user/nick/updates'
+  branch: 'user/nick/updates',
+  gh_token: ''
 }.freeze

lib/up2date.rb

@@ -0,0 +1,39 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+# frozen_string_literal: true
+
+require 'net/http'
+require 'json'
+require_relative '../config/config'
+
+module SlackBuilder
+  GITHUB_QUERY = <<~GQL
+    query ($name: String!, $owner: String!) {
+      repository(name: $name, owner: $owner) {
+        refs(last: 1, refPrefix: "refs/tags/", orderBy: { field: TAG_COMMIT_DATE, direction: ASC }) {
+          nodes {
+            id,
+            name
+          }
+        }
+      }
+    }
+  GQL
+  private_constant :GITHUB_QUERY
+
+  # Request the latest tag in the given repository.
+  def self.github_latest_tag(owner, name)
+    post_data = {
+      'query' => GITHUB_QUERY,
+      'variables' => { 'name' => name, 'owner' => owner }
+    }
+    uri = URI('https://api.github.com/graphql')
+    response = Net::HTTP.post uri, post_data.to_json, {
+      'content-type' => 'application/json',
+      'authorization' => "Bearer #{CONFIG[:gh_token]}"
+    }
+    JSON.parse(response.body)['data']['repository']['refs']['nodes'].first['name']
+  end
+end