GitHub apply dark theme on private repo

github-apply-dark-theme-on-private-repos.user.js

// ==UserScript==
// @name         GitHub apply dark theme on private repo
// @namespace    https://github.com/benok/
// @description  Apply dark theme to your private repository pages on Github
// @match        https://github.com/*
// @run-at       document-start
// @version      2025.4.11.3
// @homepage     https://gist.github.com/benok/301f7a9667a598202f10111af054ae77
// @downloadURL  https://gist.github.com/benok/301f7a9667a598202f10111af054ae77/raw/github-apply-dark-theme-on-private-repos.user.js
// @updateURL    https://gist.github.com/benok/301f7a9667a598202f10111af054ae77/raw/github-apply-dark-theme-on-private-repos.user.js
// @author       benok
// @grant        none
// @license      MIT
// ==/UserScript==

let apply_theme = function()
{
    // lock icon exists in repo header
    if (document.querySelector("a.AppHeader-context-item svg.octicon.octicon-lock") != null) {
        console.log('private repo. set data-color-mode to dark');
        document.querySelector('html').setAttribute('data-color-mode', 'dark');
    } else {
        console.log('public repo. set data-color-mode to light');
        document.querySelector('html').setAttribute('data-color-mode', 'light');
    }
};

let make_private_buttons_black = function(observer, elem)
{
    if (observer != null) {
        observer.disconnect();
    }

    console.log('make_private_buttons_black()');
    let lbs = document.querySelectorAll("span.Label");

    for (const lb of lbs) {
        if (lb.textContent.includes('Private')) {
            lb.style.cssText += 'background-color:#434343; color:#ffffff;'
            //lb.closest('.private').style.cssText += 'background:#cfcfcf;'; // done by css
        }
    }

    if (observer != null) {
        observer.observe(elem, {
            subtree: false,
            attributes: true
        });
    }
}

function hook_body_attr_change(hook) {
    // https://stackoverflow.com/a/11546242/26736
    let MutationObserver = window.MutationObserver || window.WebKitMutationObserver;

    let observer = new MutationObserver(function(mutations, observer) {
        hook();
    });
    observer.observe(document.body, {
        subtree: false,
        attributes: true
    });
}

function on_load() {
    console.log('on_load()');
    let user_repo_list = document.querySelector('#user-repositories-list');
    if (user_repo_list != null) {
        console.log('found user repo list');
        make_private_buttons_black(); // call once
        hook_user_repo_list_change(user_repo_list, make_private_buttons_black);
    }
}

function hook_user_repo_list_change(elem, hook) {
    console.log('hook_user_repo_list_change');
    let MutationObserver = window.MutationObserver || window.WebKitMutationObserver;

    let observer = new MutationObserver(function(mutations, observer) {
        console.log('observer handled.');
        (function (obs,elm) {
            obs.disconnect(); // hook modifies elem. need to disconnect before call
            hook();
            obs.observe(elm, {
                subtree: true,
                attributes: true
            });
        })(observer, elem);
    });
    observer.observe(elem, {
        subtree: true,
        attributes: true
    });
}

function append_css() {
    const el= document.createElement('style');
    // make private repo's bacground gray
    el.textContent = 'li.private {background-color: #cfcfcf}';
    document.head.appendChild(el);
}

(function() {
    'use strict';
    append_css();
    hook_body_attr_change(apply_theme);
    window.onload = on_load;
})();

Having trouble now.
Setting html's data-color-mode doesn't update the actual page theme. :-(
(Setting the default theme to dark, it works partially, but unstable. May be needed to change apply timing.)

Please choose "Sync with system" from Theme preferences and get this script working again.