gnome3: add updateScript

pkgs/desktops/gnome-3/default.nix

···
-{ pkgs }:
+{ pkgs, lib }:
 
 let
 
···
     in newself;
 
   callPackage = pkgs.newScope self;
+
+  # Convert a version to branch (3.26.18 → 3.26)
+  # Used for finding packages on GNOME mirrors
+  versionBranch = version: builtins.concatStringsSep "." (lib.take 2 (lib.splitString "." version));
+
+  updateScript = callPackage ./update.nix { };
 
   version = "3.26";
   maintainers = with pkgs.lib.maintainers; [ lethalman jtojnar ];

pkgs/desktops/gnome-3/find-latest-version.py

···
+import argparse
+import json
+import requests
+import sys
+
+def version_to_list(version):
+    return list(map(int, version.split('.')))
+
+def odd_unstable(version_str, selected):
+    version = version_to_list(version_str)
+    if len(version) < 2:
+        return True
+
+    even = version[1] % 2 == 0
+    if selected == 'stable':
+        return even
+    else:
+        return not even
+
+def no_policy(version, selected):
+    return True
+
+version_policies = {
+    'odd-unstable': odd_unstable,
+    'none': no_policy,
+}
+
+def make_version_policy(version_predicate, selected):
+    return lambda version: version_predicate(version, selected)
+
+parser = argparse.ArgumentParser(description='Find latest version for a GNOME package by crawling their release server.')
+parser.add_argument('package-name', help='Name of the directory in https://ftp.gnome.org/pub/GNOME/sources/ containing the package.')
+parser.add_argument('version-policy', help='Policy determining which versions are considered stable. For most GNOME packages, odd minor versions are unstable but there are exceptions.', choices=version_policies.keys(), nargs='?', default='odd-unstable')
+parser.add_argument('requested-release', help='Most of the time, we will want to update to stable version but sometimes it is useful to test.', choices=['stable', 'unstable'], nargs='?', default='stable')
+
+
+if __name__ == '__main__':
+    args = parser.parse_args()
+
+    package_name = getattr(args, 'package-name')
+    requested_release = getattr(args, 'requested-release')
+    version_predicate = version_policies[getattr(args, 'version-policy')]
+    version_policy = make_version_policy(version_predicate, requested_release)
+
+    # The structure of cache.json: https://gitlab.gnome.org/Infrastructure/sysadmin-bin/blob/master/ftpadmin#L762
+    cache = json.loads(requests.get('https://ftp.gnome.org/pub/GNOME/sources/{}/cache.json'.format(package_name)).text)
+    if type(cache) != list or cache[0] != 4:
+        print('Unknown format of cache.json file.', file=sys.stderr)
+        sys.exit(1)
+
+    versions = cache[2][package_name]
+    versions = sorted(filter(version_policy, versions), key=version_to_list)
+
+    if len(versions) == 0:
+        print('No versions matched.', file=sys.stderr)
+        sys.exit(1)
+
+    print(versions[-1])

pkgs/desktops/gnome-3/update.nix

···
+{ lib, writeScript, python3, common-updater-scripts, coreutils, gnugrep, gnused }:
+{ packageName, attrPath ? packageName, versionPolicy ? "odd-unstable" }:
+
+let
+  python = python3.withPackages (p: [ p.requests ]);
+in writeScript "update-${packageName}" ''
+  set -o errexit
+  PATH=${lib.makeBinPath [ common-updater-scripts coreutils gnugrep gnused python ]}
+  latest_tag=$(python "${./find-latest-version.py}" "${packageName}" "${versionPolicy}" "stable")
+  update-source-version "${attrPath}" "$latest_tag"
+''