heroku: add updateScript

pkgs/development/tools/heroku/default.nix

@@ -1,19 +1,12 @@
-{ stdenv, lib, fetchzip, makeWrapper, nodejs }:
+{ stdenv, lib, fetchzip, makeWrapper, nodejs, writeScript }:
 
-let
-  # version and commit pairs can be found in the URLs at
-  # https://cli-assets.heroku.com/versions/heroku-linux-x64-tar-xz.json
-  version = "8.7.1";
-  commit = "3f5e369";
-  hash = "sha256-3pCutQBS8N1Yw4JKTvU046UrOxBi0wLRQywxwezAEeU";
-in
 stdenv.mkDerivation {
   pname = "heroku";
-  inherit version;
+  version = "8.7.1";
 
   src = fetchzip {
-    url = "https://cli-assets.heroku.com/versions/${version}/${commit}/heroku-v${version}-${commit}-linux-x64.tar.xz";
+    url = "https://cli-assets.heroku.com/versions/8.7.1/3f5e369/heroku-v8.7.1-3f5e369-linux-x64.tar.xz";
-    inherit hash;
+    hash = "sha256-3pCutQBS8N1Yw4JKTvU046UrOxBi0wLRQywxwezAEeU=";
   };
 
   nativeBuildInputs = [ makeWrapper ];
@@ -29,6 +22,19 @@ stdenv.mkDerivation {
       --set HEROKU_DISABLE_AUTOUPDATE 1
   '';
 
+  passthru.updateScript = writeScript "update-heroku" ''
+    #!/usr/bin/env nix-shell
+    #!nix-shell -I nixpkgs=./. -i bash -p nix-prefetch curl jq common-updater-scripts
+    resp="$(
+        curl -L "https://cli-assets.heroku.com/versions/heroku-linux-x64-tar-xz.json" \
+            | jq '[to_entries[] | { version: .key, url: .value } | select(.version|contains("-")|not)] | sort_by(.version|split(".")|map(tonumber)) | .[-1]'
+    )"
+    url="$(jq <<<"$resp" .url --raw-output)"
+    version="$(jq <<<"$resp" .version --raw-output)"
+    hash="$(nix-prefetch fetchzip --url "$(jq <<<"$resp" .url --raw-output)")"
+    update-source-version heroku "$version" "$hash" "$url"
+  '';
+
   meta = {
     homepage = "https://devcenter.heroku.com/articles/heroku-cli";
     description = "Everything you need to get started using Heroku";