update source attributes other than src

[Artturin]

Motivation is to update packages such as catppuccin CC @khaneliman and lambda-lisp CC @cafkafk

Diff Setting bat source to an old version and adding sources to passthru

diff --git a/pkgs/data/themes/catppuccin/default.nix b/pkgs/data/themes/catppuccin/default.nix
index 16befcd06b81..46214c6ed74b 100644
--- a/pkgs/data/themes/catppuccin/default.nix
+++ b/pkgs/data/themes/catppuccin/default.nix
@@ -20,8 +20,8 @@ let
       name = "bat";
       owner = "catppuccin";
       repo = "bat";
-      rev = "ba4d16880d63e656acced2b7d4e034e4a93f74b1";
-      hash = "sha256-6WVKQErGdaqb++oaXnY3i6/GuH2FhTgK0v4TN4Y0Wbw=";
+      rev = "00bd462e8fab5f74490335dcf881ebe7784d23fa";
+      hash = "sha256-yzn+1IXxQaKcCK7fBdjtVohns0kbN+gcqbWVE4Bx7G8=";
     };
 
     bottom = fetchFromGitHub {
@@ -102,6 +102,8 @@ stdenvNoCC.mkDerivation {
     runHook postInstall
   '';
 
+  passthru = { inherit sources; };
+
   meta = {
     description = "Soothing pastel themes";
     homepage = "https://github.com/catppuccin/catppuccin";

nix-update "catppuccin" --src-attr "sources.bat"

It would be nice to be able to use nix-update to update such sources instead of a custom update script

Related #163 because being able to pass catppuccin.sources.bat would fix this issue too.

[Artturin]

Currently fails with

nix_update.errors.VersionError: Please specify the version. We can only get the latest version from codeberg/crates.io/gitea/github/gitlab/notabug/pypi/savannah/sourcehut/rubygems projects right now

[Artturin]

Output of the pprint(package)

Package(attribute='catppuccin',
        name='catppuccin-unstable-2023-10-09',
        old_version='unstable-2023-10-09',
        filename='/home/artturin/nixgits/my-nixpkgs/pkgs/data/themes/catppuccin/default.nix',
        line=19,
        urls=['https://github.com/catppuccin/bat/archive/00bd462e8fab5f74490335dcf881ebe7784d23fa.tar.gz'],
        url='https://github.com/catppuccin/bat/archive/00bd462e8fab5f74490335dcf881ebe7784d23fa.tar.gz',
        src_homepage='https://github.com/catppuccin/bat',
        changelog=None,
        rev='00bd462e8fab5f74490335dcf881ebe7784d23fa',
        hash='sha256-yzn+1IXxQaKcCK7fBdjtVohns0kbN+gcqbWVE4Bx7G8=',
        go_modules=None,
        go_modules_old=None,
        cargo_deps=None,
        npm_deps=None,
        yarn_deps=None,
        tests=[],
        has_update_script=False,
        parsed_url=ParseResult(scheme='https', netloc='github.com', path='/catppuccin/bat/archive/00bd462e8fab5f74490335dcf881ebe7784d23fa.tar.gz', params='', query='', fragment=''),
        new_version=None,
        version_position=Position(file='/home/artturin/nixgits/my-nixpkgs/pkgs/data/themes/catppuccin/default.nix',
                                  line=66,
                                  column=3),
        cargo_lock=<nix_update.eval.NoCargoLock object at 0x7fc032a9e150>,
        diff_url=None)