Loading emacs themes or plugins from version control

With emacs 30, use-package got an extension that allows for the use of version control:

(use-package catgirl-theme
  :vc (:url "https://codeberg.org/LunarWatcher/catgirl.el.git"
            :rev :newest)
  :ensure t
)

Not sure if these can be upgraded with the same command as everything else, but there is M-x package-vc-* variants of the upgrade commands (M-x package-vc-upgrade-all) that do bump them as expected.

Note that the name passed to use-package matters a fair bit, as it's reused by use-package to determine which file is loaded. In this case, if catgirl was used as the package name, the theme would fail to load because the name of the file is catgirl-theme.el.