youtrack-git-branch.user.js

// ==UserScript==
// @name         YouTrack - Git Branch
// @namespace    http://tampermonkey.net/
// @version      0.1
// @description  Based on current YouTrack Ticket and logged in user, copy git branch command to the clipboard
// @author       Stepan Riha
// @match        https://*.myjetbrains.com/youtrack/issue/*
// @run-at       context-menu
// @grant        GM_setClipboard
// ==/UserScript==

(function() {
    'use strict';

    var $name = document.querySelectorAll('[data-test="ring-dropdown ring-profile"]')[0];
    var issueid = location.pathname.split("/").pop() || "";
    var branch = "";
    var inls = "";

    if ($name && issueid.match(/-\d+$/)) {
        inls = ($name.title || "").split(/\s+/).map(s => s[0] || "").join("").toLowerCase();
        branch = inls + "/" + issueid;
    } else {
        console.log("could not create branch name", { $name, issueid });
    }

    if (branch) {
        var cmd = "git checkout -b " + branch;
        GM_setClipboard(cmd, 'text');
        alert(cmd);
    }
})();